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Full text of "Practical Electronics 1968 June"

PRACTICAL 






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SOLDERING EQUIPMENT 
for Ike 

DISCRIMINATING 
ENTHUSIAST 




ILLUSTRATED: 

L64 &" BIT INSTRUMENT IN 

L700 PROTECTIVE SHIELD 

APPLY DIRECT TO: 

SALES & SERVICE DEPT. 
ADCOLA PRODUCTS LTD. 
ADCOLA HOUSE 
GAUDEN ROAD 
LONDON, S.W.4 
TELEPHONE 01-622 0291 



TWO-YEAR GUARANTEE 

EX-RENTAL TELEVISIONS 

FREE ILLUSTRATED 

LIST OF TELEVISIONS 

17"— I r— 21"— 23* 




WIDE RANGE OF MODELS 

SIZES AND PRICES 

DEMONSTRATIONS DAILY 



1 7in.— £11.10.0 

3 Star Guarantee 

* Tube * Valves 

-£ Components Carr. 30/- 

TRANSISTOR CHASSIS 

59/6 
6 Transistors. LW/MW. Tele- 
scopic Aerial. Brand New. 
Famous British Manufacturer, 
(LESS SPEAKERS) P. & P. 4/6. 
SINGLE PLAYER 

CABINETS 19/6. P. & P. 7/6. 
TRANSISTOR CASES 19/6. 
Cloth covered, many colours. 
Size 9 T " X *t*X 3t*. .P. & P- 3/6. 
Similar cases in plastic 7/6. 



£19 
STEREOGRAM CABINET 

An elegant Stereogram Cabinet 

in modern Veneered Mahogany 

and cloth covered Front Panel 

BLACK LEATHERETTE SIDE PANELS 

Dimensions: 52" x I7i* x 12* 

Speaker positions for Twin 

10* x 5* Speakers 




OTHER MODELS— SEND FOR LIST 



RADIOGRAM CABINETS 
ONLY £5.19.6 




An attractive discreetly 
designed space saying 
cabinet in natural grained 
polyestered sapcle. Press- 
drop flap for autoehanger 
and record storage com- 
partment. 10* x 5* speaker 
position. Complete with 
legs. Dim. 291*HxM|-D 
x 29* W. Carr. Ins. 25/-. 



DUKE & CO. (LONDON) LTD. 

621/3 Romford Road, Manor Park, E.12 

Phone 0M78 6001-2-3 Stamp for Free List. 



BRAND NEW PARMEKO HT TRANSFORMERS 

Pri tapped MO-2s0VV Sec. 500-0-500 V. 250mA. 6-3 V 4A. 6 3V 1-5A. 63V 4A, 

5V 3-5A. Metal cased table top connections. Fraction of maker s price 
£4.15.0; carr. 10/-. 

BRAND NEW TWICKENHAM HEAVY DUTY L.T 

PrT*pp S ed°| R M 2 E 20 S 23S, 250V. Sec. No. I, S5V 24A. Sec. No. 2. 14V I0A. 
See. No. 3. 60V 2A 1 1-0-OV 2A. Tropically finished—terminal connections. 
Fraction of maker's price £9.19.6; carr. IS/-. 

HEAVY DUTY L.T. TRANSFORMERS 

Pri 220-240V Sec. 12V, 90A, Flying lead connections. £13.19.6; carr. 10/6. 
Pri tapped 190, 210. 230, 250 V. Sec, 55 V, 50 A £18.10.0; carr. IS/-. 

L, T. SUPPLY UNITS TYPE S.E.S . 

A.C. input 220-240 Vd.c. Output 12 or 24V I0A continuous rating. Selenium 
full wave bridge rectification. 3 inch scale ammeter, neon indicator, housed 
in strong metal case. Size 17 x 7 x 6Jin. £14/10/-; carr. 15/- 

VAR1ABLE D.C. SUPPLY UNITS TYPE SE.4. 

0-46V I0A continuous from 240V a.c. Silicon full wave bridge rectification, 
isolated transformer with Variac controlled primary 3 inch scale voltmeter 
and ammeter. Neon indicator. Housed in strong metal case. Sue 
17 x 7 x djin. £19/10/-; carr. 15/- 

ADVANCE COMPONENTS LTD. _. 

Stabilised low voltage power supply units. Type DC J. '"P ut 
200-2 1 S-230-245V, Output 12V. I-2SA at 55°C. stabilised within —1% at 
full load with supply voltage variation up to ± 15%. Ripple less than I -5 / 
R, M.S. of total output. Supplied brand new, £5.10.0; carr. 10/-. 

WONDERFUL OFFER! 
SCOTCH MAGNETIC TAPE. Type 3 M 459. *in 3,600 feet. Suitable 
for video. Brand new in maker's sealed cartons. List Price £18/10/-. 
Our Price £3/19/6. P.P. 5/-. 

SPECIAL OFFER OF BLOCK CAPACITORS 

BRAND NEW IN MAKER CARTON 
G.E.C. BmF 600V d.c. wkg. at 7I*C. Six for 19/6. Cam W*. S.T.C, 
5mF 400V a.c. wkg., three for 17/6. Carr. 7/6. S-2SmF 600V a.c. wkg„ 
three for 22<6. Carr. 7/6. Aerovox ImF 600V d.c. wkg., six for 12/6. 
P.P. 4/6. T.M.C, 2mF 100V d.c. wkg,, six for 7/6. P.P. 4/6. 



SAMSO N'S (ELECTRO N 1CS) 

9-10 Chapel Street, 
London, N.W.I 

Tel: PADdington 7851 
AMBassadar 5125 



LTD. 



DON T IV 



\ HAVE YOU GOT YOUR LASKY'S CATALOGUE ± 

/" CDEC Second Brest Reprint Issue How Rudy. 
r ■ r» C C j u ,t Ka & y0U r name, address and 1 :- for vast only. ^s 




ITEMS 



DESIGNED ESPECIALLY TO REPLAY 

PHILIPS CASSETTE SYSTEM 

THE FANTAVOX 

TAPE CASSETTE PLAYER 

This machine is the ilrat of iU type ami is designed speci- 
fically to replay pre-recorded tape casse! tea made for the 
PHILIPB :m:l other caaaette systems. The cassette is 
simply slipped Into the machine and is immediately ready 
to play. Each cassette gives over 40 minutes play (twin 
track), no loss ot time in rewinding— simply turn cassette 
over. Constant tape speed 1 } i.p.s. Only two controls off, 
piny and vol. Full}* transistorised, powerful vol., built in 
speaker, socket for personal earpiece. Operates on l> iten- 
llght batteries. Verv attractively styled shockprool pUwtii 
cabinet slie lit : 4{ X 21n with wrist utrap. Complete with 
earpiece and batteries. There are now over 200 inusi- 
i -asset tc titles available: tazz, pop, shows and classics. 
This machine allows you to piny the inusie of jour choice 
anywhere— anytime. 

LASKY'S PRICE £7.9.6 jw- 

CROWN MODEL TRF-6 AM/FM 
9 TRANSISTOR RADIO 

Unbelievably small tor an AMjFM receiver— the 
Crown Is only 4 J In x 21 in St 13 in. Super sensitive 
'J transistor superhet circuit with dlrectionles>- 
nUblltsed reception. AM cover: MW 335-1 ,60 5k c/s. 
FM cover; B8-108Mc/s. Superb tone reproduction. 
2 i In PM speaker. Precision tuuinsr. R section 
1 14 Jin) telescopic aerial— clips into side when 
not in use. Output 280mW mas. Beautifully 
styled and finished cabinet in black plastic with 
silver inclol trim. Operates on one 9V battery. 
Complete with leather purse, ear-piece and battery. 
Lure Price 13; Gns. 

SCOOP Price £7.19.6 ^w 
MODEL C-I000 MILI TESTER 

A real I v 1 1 n v m e t e r w I lb " b is" meter performance . Br ief Spec] flea 
lion: Muvcuient sensltivitv lOtVM. DC. volte ranges: 0-10, BO. 25(1 
1,000 volts, + 3% fsd at IK OPV. A.C. volts ranges: 0-10, oO 
260, 1,000 volts + 4% fad at IK OPV. D.C current: 0-1, 100mA 
Resistance range; 0-JnOkn. Size 2Hn : 3Jin A lin. 

Lasky's Price 39/6 tu*m 

AUDIO GENERATOR Model TE-22 

A new factory tested and calibrated low 
distortion Sine wave and Square wave 
Audio Generator suitable for use with most 
oscilloscopes. Brief Specification : fre- 
quency range. Sine wave 20c/s to 200kc/6 
in four switched ranges 20-20Gc,fs, 200c/s 
to 2kc[s, 2-20ke/B. 20-200ke;s. (Two 
scales 10-90 and 20-200 on etched circular 
dial with hair-line cursor.) Square wave 
range BOc/s to 30ke/s (read on same scales 
as Sine waves). Frequency response 
6<kVs to lSOkc.'s ± 1MB. Distortion 
less than 2%. Output voltage: load 
Impedance IMQ, 7V (msi.). load impe- 
dance 10k n, 6 V (max.). Variable 
output amplitude control. Valve line-up: 
DBMS, 12AT7, 8X4. Power requirements 
108/12oV or 220/240V, 50;e0e/B a.c. Strong 
metal cabinet size 7 X 10J x B|in, finished in 
(trey crackle with leather carrying handle. 
Power "on" pilot light fitted. Complete 
with teat leads and instruct ion book. 



rifiMiiiiire 



EA5UR 





"EASI-TUNE" AM/FM MAJOR 

V.H.F. CAR RADIO 

A completely new British 
made AM/FM car radio 
that brings the Hi-Fi 
quality of FM trans- 
missions to your car 
(ALL the new local 
stations) 1'IA'S medium 
waveband cover 185- 

570m and long wave- 
band cover 1 ,15*-2,OOOm 
(FM cover: 8-108Mc;s 
with automatic. A.F.C.), 
Featurea five EAS1TUNE 
push button* for wave 
tioti of three ot vour favourite medium wave stations, plus full 
Nine transistor and tour diode circuit gives immediate reception. 




, h».r*< 



rlnl BIW output and superior performance at high speed. Other features ineludr 
[,!:,!, ,filial. red ■■on" indicator, tone control. Strong metal case size / 2 J Sj.ln 
,11 standard wit -outs). Very handsome appearance, si h-er, black,' chrome limsh. ror 



Jin. speaker, baffle board, 




Lasky's Price £15.0.0 Post 5 



mm ,.■■;:, 1 tuning 
powerful 

llmi:lh 

(fits all L 

12 V positive or negative earth operation. Complete w 
universal mounting kit and instruction manual. 

LASKY'S PRICE 23 Gns. pqu free 
k ir\A# ANOTHER "EASI-TUNE 
INCW CAR ENTERTAINER 

THE STEREO-TONE 

STEREO TAPE 
CASSETTE CAR 
PLAYER 

Another British llrst- 
rlght on time, right up- 
to-date the latest in 
travelling pleasure. Plays 
ALL the new great 
range of PHILIPS 
MusicasselUs with over 
250 1 it lea now available— 
giving YOU the choice 
of music lor your 
Journey (each cassette 
gives up to 48m In 

Cr^ U T°o U ne!s ll eo m pact ) ,%a S y to fit and styled to enhance any car. Incorporate, the 
weiroroven Fbil?p^ape plav rnechanism and a specially developed 12 transls or ampli- 
Her ehTnc^W output jS channel with sharp stereo separation. Controls Inclmk 
.n'oft with indicator, single control for start.stop, fast forward and rewind, sep. volume, 
l-nis, treble and stereo balance controls. Tape loading ami change are super easy- 
Ihc Stereo-Tone slides out from i.a vibration free mounting or inserting or l"'»i« 
cJMsetle over then pushes back for obstruction free operation. The Mcreo-Tone 
cXet l» made Iron? hich quality scratch proof CVCOLAC plastic to ***£« *± 
wtin silver control panel with black knobs. Size only u; a i ,1 n. Tape speed 
U I p with tran 8 r 8 t„r motor regulator. Operates on all I2t IMrftlve or nega ll« 
earth syaterns. Complete with two loudspeakers, baffle board*, leads, etc., simple 
(four screw fixing) mounting assembly AMD one Free Musicassettc of your choice 

LASKY'S PRICE £29.0.0 post free 

TWO BAND TRANSISTOR CAR RADIO BARGAIN ! 

MODEL CR-62 

A new high quality imported all transistor 
auperhct car radio that really breaks the 
riual ity/p rice barrier. A unique feature of 
this set are the four M,'W band station pre- 
selection buttons which you yourself set to 
your own four favourite stations — this is in 
addition to full MfW band cover over 
830-1 ,ttOekc/s and full LfW band cover over 
100-300ke/« (IF frequency 453kc/s). Ester- 
nallv adjustable aerial trimmers ensure 

maximiJ output. Si. transistor, th^tag.uu, drift J_ype>_ and ^jji^^* 
provides powerful 2\V output. 




The set is adjustable for" use on either positive or 



installation Instructions 

uarantenl. 



3| * 01 * ™n- Irntit panel Jin larger all round -finished in anodised aluminium with 
black push buttons. Complete with mounting brackets, tu 
and two baffle boards (for round or elliptical speaker). Fullv 

LASKY'S PRICE £9.19.6 tots/* 

6 : tin elllptieil 8n rlyn«mic speaker 17/6 extra- Post FREE. 

SPECIAL OFFER -LOCKIH& CAR AERIAL Model S3003 fiyc section «M "'««'"•' 
heavv chrome telescopic wins mounting type with un.que locking device to protect the 
antenna wh"n closet. Complete with mounting bracket, lend and plug and two Keys . 
LASKY'S SPECIAL PRICE 39 ■« Post Free with the Royal CK-62. . Post Sep. 2;(5 



207 EDGWARE ROAD. LONDON. W.2 Tel.: 01-723 3271 42 TOTTENHAM CT. RD.. LONDON, W.I Tel: 01-580 2573 

Open .ill ,1,,, Saturday earty clostng ' " m Thuisdey Opon dl) dsy'Thursdav. fariv closinq 1 pm Saturday 

33 TOTTENHAM CT. RD„ LONDON. W.I Tel,: 01-636 2605 

, rjay, 9 ,i m -6 pm Mnr-i.v, .0 sawrday 1)8 EDGWA RE ROAD, LONDON. W.2 Tel.: 01-723 9789 

152/3 FLEET STREET, LONDON, E.C.4 Tel.: FLEel St. 2833 0(if;n „, d v Sr „, jv .,,. , . T11 Thursd;iy 

Opon all day Thur^d-iv. pnriv closirig 1 p ni SaturrJ I . 

ALL MAIL ORDERS AND CORRESPONDENCE TO: 3 15 CAVELL ST., TOWER HAMLETS, LONDON, E.I Tel.: 01790 4821 



118 EDGWARE ROAD, LONDON. W.2 Tel.: 01-723 9789 



385 



PP3 Eliminator. Flaj- your pocket radio 
Irom toe mains! Save £a. Complete 
component kit comprises 4 rectifiers— 
mains dropper resistances, smoothing 
condenser and instruct lone. Only 6/9 
plus 1/. post. 



MINIATURE WAFER SWITCHES 



4 pole, 2 way — 3 pole, 3 way — 4 pole,, 
3 way — 2 pole, 4 way — 3 pole, 4 way 
—2 pals, 6 way — 1 pole, 12 way. All 
at 3/8 each, 36/- dozen, your assort- 
ment. 




DRILL CONTROLLER 

K tec ironically changes speed from appftmrnsiLely 
10 revs, to maximum. Full power at all speed a by 
finger-tip control. Kit Includes all parte, case* every- 
thing iiml lull JnetruC' 
tiou« IBIS plus 2/6 post, 
Hud insurance. Or 

available made up 32/8. 
Pius 2/fl post and ins. 



WATERPROOF HEATING ELEMENT 

26 yarda length TOW. Self-regulating 
temperature control. 10/- post free. 





INFRARED BINOCULARS 



CENTRIFUGAL FAN 

Centrifugal blower or extractor by Totrliigton, 
very low noU£ bat large en purity air flow, designed 
for renin* I heating and air conditioning. Ideal 
afeo for fume extraction uver cooker, duct type 
i ml let, 200; 500 V on vft iiitrtor. £3.19,6. Fcwt 
and iiiHurance 7/6, 




A.E.I. FRACTIONAL H.F, MOTOR. 200/2S0V 

60/60 c/a t'uclcsed continuous rating 1/40 h.p, 

Ex. equip , perfect order. 19/8 plut 4/6. 

A.C. FAH. Powerful mains motor with 6iln. blade. 

Ideal blow or extract. 17/8 plus 3/fi. 

1 27 MICK EL CADMIUM CELLS. I* in- Jin. by 

Jin. thick (approx.). 8/6 each. Charger for two 

cells 12/6. 

OIL THERMOSTAT. Tedd iogton type T.B.B. with 

capillary tube and sensor adjustable by knob (not 

supplied) controls J h.p. motor or up to 15 amp. 

resistive load. 9/0, 

5 PUSH SWITCH. One push operates mains on/off 

awitch the other four operate various on/off ami 

change/over switches. 2/6. ' 



QUICK CUPPA 

Mini Imimrrsioti Heater, 300 W, 
200/240 V. Bulla full cup In 
about two uduule«. Use any 
socket or tat up- holder. Have 
at bedside for tea, baby's food, 
etc. 19/6, post and Insurance 1/6, 



NO SOLDERING 
POCKET 3 

Lots of fun to build 
and good results when 
finished. Complete 
kit with detailed Instruc- 
tions and crystal earpiece. 
Batteries 1/2 extra— «5 value 
only 19/6, plus 3/- post and ins 



THIS MONTH'S SNIP" 

Futl-Fi 12in. loudspeaker. This is undoubtedly one of 
the finest Juudspeakers that we have ever offered, 
produced by one of this country's most famous makers. 
It has a die-cast metal frame and Is strongly recom- 
mended for Hi-Fi load and Rhythm Guitar and public 
address. Flux Density 11.000 gauss — Total Flux 
44,000 Maxwells; Power Handling 15 watts r.ni.s.; 
Cone Moulded fibre; Freq. response 30-10,000 e/«; 
Input Impedance 15 ohms; Main resonance 60 c/s; 
Chassis Diam. 12ln. — 12 Sin. over mounting lugs; 
Baffle hole 11 in. diam,; Mounting holes 4 — Holes }iu. 
diam. on pitch cirele 1 IJin. diam,; Overall height GJIii. 
A £6 speaker offered for only 13,9.6 plus 7/6 post and insurant 





GARRARD 

AUTO RECORD PLAYER 

Model 3000 

This is one of the latest products ol the 
World's most experienced maker of fine 
record reproducers. Its superior features 
include — automatic playing of up to w 
mixed feize records — stopping and start! tig 
without rejecting - manual playing — pick-up 
pivots to give low stylus pressure — large dia- 
meter turntable fur max. stability. Adjustments include pick-up height— pick-up 
dropping position and stylus pressure. Sise is 13J ■: 11 jin. clearance 43 in. above, 
2Jin. below. Fitted with the very superior ceramic stereo cartridge type 9TAHC 
with diamond sly III which is listed at over £4. Price complete 410.9.6, earr. and 
insurance 7/6. 




These ttilra-red binoculars when fed from a high 
voltage source will enable ubjects to be seen In the 
dark, provided the objects 'arc in the rays of an 
infra-red beam. Each eye tube contains a complete 
optical lens system as well as the Infra-red cell. 
These optical systems can be used as lenses for 
TV cameras— light cells, etc. (details supplied). 
The binoculars form part ol the Army night driving 
(Tabby) equipment. They are unused and believed 
to be in good working order but sold without a 
guarantee. Price £3,17.6, plus 10/- carr. and Ins. 
Handbook 2. ; ri 

MAINS MOTOR 

Precision made — as used 
in record decks and tape 
recorders — Ideal also for 
extractor fans* blower, 
heater, etc. New and 
perfect. Snip at 9/6, 
Postage 3}* for first 
one i hen 1/- for each 
one ordered. 12 
aud over post 
free, 

MAINS TRANSISTOR 
POWER PACK 

■Designed to operate translator sets and amplifiers. 
Adjustable output BV, HV, 12V for up to 500mA 
(class B working). Takes the place of any of the 
following batteries: PP1, PP3, PP4, PP6, PPT, 
PP9 and others. Kit comprises': mains transformer 
rectifier, smoothing and load resistor, condensers 
and instruct Inns, Real snip at only 18/8 plus 3/6 
postage. 




Where poBtage is not definitely stated as an 
extra then orders over £3 are post free. Below 
£3 add 2/9. Semiconductors add 1/- poet. 
Over f 1 post free. S.A.E. with enquiries please. 



ELECTRONICS (CROYDON) LIMITED 

(Dept. P.E.) 102/3 TAM WORTH RD., CROYDON, SURREY (Opp. W. Croydon Stn.) 

also at 266 LONDON ROAD, CROYDON, SURREY SAC. with enquiries please 



MARTIN 

IS HIGH FIDELITY 

plus 



ADD-ON-ABILITY 
THRILLING POWER 
DEPENDABILITY 
GENUINE ECONOMY 



How would you like to start with 
a simple amplifier, say, and add to 
it until it became a fully stereo 
twenty watt amplifier with FM 
tuner and facilities to take the most 
sensitive low output pickups ever 
made? With Martin Audiokits 
it's easy, for with these superbly 
engineered ail-transistor prefabri- 
cated units, success is built in from 
the start and you build to your own 
preferred plan. IT'S A MONEY 
SAVING SCHEME, TOO. 

# Trade enquiries invited. 



Details from: — 

MARTIN ELECTRONICS LTD., 1 55 Hin.li Street, 
Middlesex. iSLeworth II61 



Brentford, 



To MARTIN ELECTRONICS, 155 High Street 
Brentford, Middlesex 

l have not had your leaflets before. Please send them on 
AMPLIFIERS □ FM TUNER □ REC0RDAKITS □ 

(Tick as required) 



NAME. 



ADDRESS 



PE6 



PARKERS SHEET 
METAL FOLDING 

MACHINES 

HEAVY VICE 
MODELS 

With Bevelled Farmer Bart 

No. I. Capacity 18 gauge mild steel x 36in. wide 

No. 2. Capacity 18 gauge mild steel x 24in. wide 

No. 3. Capacity 16 gauge mild steel x I Sin. wide ... 

Also new bench models. Capacities 48in, x 18 gauge £40 

£25. 24in. x 16 gauge £24. Carriage free. 

End folding attachments for radio chassis. Tray and Box making for 36in, 

model, 5/6 per ft. Other models 3/6. The two smaller models will form 

flanges. As supplied to Government Departments, Universities, Hospitals. 

One veer's guarantee. Money refunded if not satisfied. Send for details. 
A. B.PARKER, Folding Machine Work i, Upper George Si., Heckrnondwike, Yorki. Htikmondwtke 3997 




Carr. tree 

£12.10.0 

. ... £7.5.0 
. ... £7.5,0 
36in. x 18 gauge 




SA/WNA 



TESTERS 



USED THROUGHOUT THE WORLD, 
SANWA'S EXPERIENCE OF 30 YEARS 
ENSURES ACCURACY, RELIABILITY, VER- 
SATILITY. UNSURPASSED TESTER PER- 
FORMANCE COMES WITH EVERY SAN WA 
6 Months' Guarantee ' Excellent Repair Service 

Model P-iB £3 7 6 

Model JP-5D £5 10 

Model U-50D £7 5 

Model 360-YTR £7 t7 6 

Model 3B0-CD £13 5 

Please write for illustrated leaflets of these 
Sanwa Meters 



SOLE IMPORTERS IN U.K. 



QUALITY ELECTRONICS LTD. 

47-49 HIGH STREET. KINGSTON- UPON -THAMES. SURREY Tel: 01-546 4585 



386 




plug in 

the smallest 
soldering iron 

available 



When you buy a British 
made Antex miniature 
soldering iron you are buying 
a specialised precision 
instrument that has proved 
its success in the majority of 
leading companies in the 
electronics industries 
throughout the World. These 
are professional irons for the 
man who wants the ultimate 
in precision soldering. The 
versatility and accuracy of an 
Antex iron will give you 
fingertip control over any 
soldering problem. Send for 
your Antex iron now. Or you 
may have our colour 
catalogue. Simply complete 
the coupon. 

CN 15 watts. Ideal for minia- 
ture and micro miniature 
soldering. 18 interchangeable 
spare bits available from .040" 
(1mm) up to 3/16". For 240, 
220,110, 50 or 24 volts. 



From Electrical and 
Radio Shops or send 
cash to Antex. 



32'6 



Complete precision 
soldering kit 




This kit — in a rigid plastic 
"tool-box" — contains 
everything you need for 
precision soldering. 

■ Model CN 15 wans 
miniature iron, fitted 
A" bit- 

■ Interchangeable spare 
bit, ■&". 

■ Interchangeable spare 
bit, &". 

■ Reef of resin-cored 
solder 

■ Felt cleaning pad 

■ Stand for soldering iron 

■ Space for stowage of 
lead and plug 

PLUS 36-page booklet on 
"How-to-Solder"— a mine 
of information for amateur 
and professional. 

From Electrical and Radio 
Shops or 
send cash 
to Antex. 



49'6 




PRECISION MINIATURE 
SOLDERING IRONS 



Antex,. Grosvenor House, Croydon, CR9 1QE 
Telephone 01-686 2774 




G 18 watts. Ideal for miniature work on 
production lines. Interchangeable spare 
bits, 3/32", 1/8*. 3/1 6*4 and 1/4". Far 240, 
220 or 110 volts. 32/6. 



E 20 watts. Fitted with 1 /4" bit. 
Interchangeable spare bits 3/32*. 1/8", 
3/1 6- . For 240, 220, 110 or 24 volts. 35/- 



ES 25 watts. Fitted with 1/8* bit. 
Interchangeable bits 3/32". 3/16" and 1/4" 
Ideal for high speed production lines. 
For 240, 220, 110. 24 or 12 volts. 35/-. 



F 40 watts. Fitted 5/16* bit. 
Interchangeable bits 1/4*. 3/1 B". 1/8", 3/32* 
Very high temperature iron. Available 
for 240, 220, 110. 24 or 20 volts. 42/6. 

Spare bits and elements for all model* 

and voltages immediately available from stock. 



To: Antex . Grosvenor House, Croydon, CR9 1QE 

I Please send me the Antex colour catalogue 
J Please sand me the following irons 

Quantity Model Bit Size Volts Price 



1 enclose cheque P.O. cash value. 

NAME 

ADDRESS 



P.E.* 



Telephone : 



387 



l i mMHii]U!ili l '!Hi'l;rH;l 



INPUT 230/2«v. A.C. 50/60— 
OUTPUT VARIABLE p-260v. 
BRAND NEW 

Keenest price* in the country. 
AH Types (and Spares) from 
7 to 50 amp. from stock. 

SHROUDED TYPE 

I amp, £5. 10. 0. 2.5 amps, 

£6, 15. 0. 4 amps, £9. 0. 0. 

5 amps, £9. 15. 0. 8 amps, 

£14. 10. 0. 10 amps, £18, 10. 0. 
[lamps, £21. 0. 0. 15 amps. 

£25. 0. 0. 20 amps, £37. 0. 0. 
37,5 amps, £72. 0. 0. 50 amps, 
£92. 0, 0. 

OPEN TYPE (Panel Mounting) 
t amp, £3. 10. 0. I amp, £5. 10. D. 
21 amps, £6. 12. 6. 

PORTABLE TYPE 
PORTABLE TYPE 1.5 amp. portable fitted metal case 




£9. 5, 0. 



voltmeter, lamp* switch, etc. £9*5,0, 
Similar to above 2.5 amp. £l 1 ,7.&. 




100 WAH POWER RHEOSTATS (NEW) 

AVAILABLE IN THE FOLLOWING VALUES 

I ohm, 10 a.; 5 ohm, 4.7 a.; 10 ohm, 3 a.; if 

25 ohm, 2 a.; SO ohm, 1.4 a.: 100 ohm, t a.; '■}[ 

250 ohm, .7 a.; 500 ohm, .45 a.; 1,000 ohm, 

280 mA; 1,500 ohm, 230 mA; 2,500 ohm, .2 a. Diameter 

3£in. Shaft length Jin., dia. A J in. All ac 27/6 each. 

P. & P. 1/6. 

50 WATT. 1/5/ 1 0/25/50/1 00/250/500/ 1, 000/ 1, 500/2.500 

ohm, 21/-. P. & P. 1/6. 

25 WATT, 10/25/50/ 1 00/250/500/ 1 ,000/ 1 ,500/2,500 

ohm, 14/i. P. & P. 1/6. 

VENNER ELECTRIC TIME SWITCH 

200-250 v. A.C. 20 amp. contacts twice on, 
twice off, at any manually pre-set time. 
Spring reserve (in case of power cut) fully 
tested £3/9/6. P. & P. 4/6. Or complete 
in weatherproof metal case (illustrated) 
£3/19/6. plus 4/6 P. & P. Can be supplied 
with solar dial, on at dusk— off at dawn. 
Prices as above. 

Afe^ FflfuLATED terminals" 






Available in red, white, yellow, black, blue 
an d green. New 17'- per doi. 2/-. P. & P. 

230/250V. A.C. SOLENOID*™ 

Heavy duty type, approx. 3 lbs. pull. Price 
17/6 plus 2/6 P. & P. 

12 24V. D.C. SOLENOID 

Appro x. 8 o z. push. Price B.'6 plus 1/6 F, & P 

" PRECISION INTERVAL TIMER 

From 0-30 seconds (repetitive). Jewelled 
balanced movement. Lever re-set. 
Operates 230V. A.C. 5 amp. c/o Micro- 
switch .New. Price 17/6 p l us 2/6 P . & P. 

CONDENSERS 2.500 mfd I00v. 12/6 1/6 P. & P. 
4.000 mfd 25v. 10/- 1/6 P. & P. 4.000 mfd 50v. 15/- 
1 /6 P. & P. 10.000 mfd 35v. IS/- 1/6 P. & P. 

CONSTANT VOLTAGE TRANSFORMER 

Input 185-250 v. A.C. Output 230 v A.C. 
Capacity 250 watt. Attractive metal case. 
Fitted red signal lamp. Rubber feet. 
Weight 17 lb. Price £1 \/ 10/0. P. & P. IS/-. 

SELENIUM BRIDGE RECTIFIERS 

30 volt 3 amp., 1 I/-, plus 2/6 P. & P. 
30 volt 5 am p.. 16 / -, plus 2/6 P. & P . 

' RADIO 
ALTIMETER 

This precision instrument, built 
to highest Ministry specification, is based on a 24 v, D.C. 
LOW INERTIA Integrating Motor. The Motor, fitted 
with gold brushes and drawing only 000 microamp at 
24 v. D.C, drives two precision pots with platinum 
wipers through close tolerance gear-trains, including 
miniature slipping clutch, combined with two sub- 
miniature pots for calibrating the electrical bridge 
circuit. The " 3 in. calibrated dial, with a number 
aperture indicating one rev, per revolution of pointer 
with maximum of 5 revs, gives an effective scale length 
of approx. 30 in. Offered at fraction of Manufacturer's 
price, 32/6. P. & P. 6/-. 





L1GHT SENSITIVE SWITCH 



f 



Kit of parts, including ORPI2 Cad- 
mium Sulphide Photocell, Relay, 
Transistor and Circuit, etc., 6-12 
volt D.C. op. price 25/- plus 2/6 
P. & P. ORP 12 including circuit, 
10/6 each, plus I/- P. & P. 
A.C. MAINS MODEL Incorpo'rates 
Mains Transformer, Rectifier and special 
relay with 3, 5 amp mains c/o contacts. 
Pric e inc. circuit 47/6 plus 2/6 P. & P. 

LIGHT SOURCE7NDPHOTO 
CELL MOUNTING! 

Precision engineered 




light source with focusible- 

lens assembly and ventilated 1 
lamp housing, to take MBC bul£. Separate 
photo cell mounting assembly for ORP, 12 
or similar cell. Both units are single hole 
fixing. Price per pair £2.15.0. P. & P. 3^/6. 

RESETTABLE HIGH SPEED 

COUNTER. 4 figure, 1,000 ohm coil. 
36-48 v. D.C. operation. £3/10/-. P. & 
P. 1/6. 3 figure. 24 v. D.C. £1/12/4. 
P. & P. 1/6. 

DRY READ SWITCHES. New 

special offer of Dry Read Switches half 

amp. Contact. Size ij JC |. 4 for 10/- 

Post Paid. ,__ 

miniature" uniselector" wrrtH 

3 banks of I I positions plus j.v-"~r~"-.. 
homing bank. 40 ohm coil, y„ jtffet-'," 
24-36 v. D.C. operation. jpw^nPf* 

Tested. 22/6. plus 2/6 P. & P. " ' <P^ 

ro"MPACr"HEAVY DUTYTvTD.cTlteLAY 
2 change over, 30 ohm coil. 7/6 each. 
P. & P. 1/6. 3 for 20/-. Post paid. 

nickel" "cadmiu m™ "battery 

Sintered Cadmium Type 1-2 v. 7AH. 
Size: height 3 J in., width 22 X l-jjr in. 
Weight: approx. 13 oz. Ex-R,A.F, 

Te5_tecL_ 12/6^ P^&P; 2£6^ 

~£?A#/ MULTI 
RANGE METERS 

New Model U50D Mutti tester, 
20,000 OPV, mirror scaled with overload 
protection. Ranges — d.c. volts: lOOmV, 
0-5 v. 5 v., 250 v., 1,000 v.; a.q. volts: 
2-5 v., 10 v., 50 v.. 250 v., 1.000 v.; D.C. 
current: 5 ,iA, 0-5 MA, 5 MA, SOMA, 
250 MA.' Complete with battery and test 
probe. £7/5/0 post- paid, Three other 
models available from stock. Descriptive 
lea flet on requ est. 

"hYrTsTOR 400 pTv"5lmp., 14/6 "" 
THYRISTOR 400 pi v, 8 amp., 28/ 6 

~ 220/240vTc COOLING UNIT""" 

2,300 r.p.m, 6" blade size. 
Smooth powerful motor. 
All metal construction. 
Continuously rated. 
Individually tested. 
Offered at fraction of 
maker's price. £2.15.0. 

P. & P. 7/6 

SANGAM0 WESTON 

Dual range voltmeter. 0-5 
and 0-100 v. D.C. FSD I m/a. 
In carrying case with test 
prods and leads, 32/6, P. & 

P. 3/6 .^ 

A.C CONTACTOR"" ' 

2 make — 2 break (or, 2 
c/o.). IS am p. contacts. 
230/240V. A.C. operation. 

Brand new. Price 22/6 plus 
1/6 P. & P. 

20 Amp LEVER MICRO SWITCH 

Brand new lever operated 

Micro Switch. 20 amp A.C. 
c/o contacts. Price 4/6 each 
plus 1/6 P. & P. 5 for £1 
Post Paid. 




% 



SERVICE TRADING CO 



All Mail Orders — Also Callers — Ample Parking Space 
57 BRIDGMAN ROAD, LONDON, W.4 Phone 995 1560 
SHOWROOM NOW OPEN CLOSED SATURDAY 

388 



Personal callers only 
9 LITTLE NEWPORT ST. 

LOUDON, YV.C.2. Tel. GER 0576 



ELECTRONIC BROKERS 

LIMITED 



&> 



quiet, t 
mbient ^ 



SYNCHRONOUS TIMING 
MOTORS BY HAY DON (illus.}. 
a high quality d.c. motor. 40o* 
torque at 3 r.p.m. 3 r.p.m. 12V, 
2 r.p.m. 6V, I r.p.m, 2BV, 1/12 
r.p.m. 12V, 1(12 r.p.m. 30V, 

1/15 r.p.m. 24V. 1/60 r.p.m. 

2BV, 1/120 r.p.m. 2BV. List £7. OUR PRICE 
£J,3.0. 

HYSTERESIS CLUTCH MOTOR with integral 
clutch allowing the motor to drop out of 
engagement with the gear train, thereby faci- 
litating easy resetting when used in timers or m 
conjunction with a light spring. 6ox torque at 
I r.p.m. 240V. SOe/s. L - left, R = right. 
15 r.p.m. L; 8 r.p.m. R and L; 6 r.p.m. L; 
4, h i, i r.p.m, L; i, £ r.p.m. R and L, A, 
ft, ft r.p.m. L. Also 126V, 50c/s, 2, i. ft, ft, 
ft, » r.p.m. 23/-. 

HIGH TORQUE INDUCTION MOTOR MP 10. 
Useful for cycle timers. Motorised valves, 
advertising display unit. 30oi/in at I r.p.m. 
2'S watts. 240 volts, SO cycles. 60 r.p.m., 
30 r.p.m,, 20 r.p.m. Right, 6 r.p.m., 4 r.p.m., 
It r.p.m., A r.p.m., ft r.p.m &"*%«" 
120V, 50 cycles. 20 r.p.m. List 35/-. QUH 
PRICE 15/.. 

LOW TORQUE HYSTERESIS MOTOR MA23 
(illus*.). Ideal for instrument 
chart drives, extremely quiet, 
useful in areas where ambient 
noise levels are low. Having a t 
high starting torque a rela- ^fc 
tlvely high inertia load can be «fT 
driven. 6oz/in at I r.p.m. 240 
volts, 50 cycles. 10 r.p.m. R; 
I r.p.m. R and L; £ r.p.m. L; i r.p.m. R; J 
r.p.m, R; A r.p.m. R; ft r.p.m. ft r.p.m., 
A r.p.m.. ft r.p.m., xsv r.p.m., „£„ r.p.m.; 
} r.p. hour, ft r.p.h., ft r.p.h.: I r.p.m., 
I i r.p.m., 2-2 way friction. 25/.. 
HYSTERESIS REVERSIBLE MOTOR. Incor- 
porating two coils. Each coil when energised 
will produce opposite rotation of the output 
shaft. 240 volt, 50 cycle. 15 r.p.m., 6 r.p.m., 
+ r.p.m., £ r.p.m., i r.p.m., A r.p.m., 120 volt, 
60 cycles, A r.p.m. 80/- reduced to 30/-. 
DELAY TIMER BN42 consisting of D.P.D.T. 
relay, a pilot duty switch, a clutch motor and an 
actuator, 240 volt, 50c 's lOmin., 13-Ssec, 
llOtee. £4.4.0. 

CYCLE TIMER (illus,}. Repeats 
a set cycle or sequence of 
twitching operations as long as 
the motor circuit is energised. 
Imin., 2min,, 3min., 4min., 
5min. 35/-. 

REPEAT CYCLE TIMERS V3CB. 
a timing motor which drives 
to actuate microswitches in a definite sequence 
for set periods of time. B microswitches. One 
minute or 2 minutes. £5.5.0. 

PROGRAMME TIHERS. 240 

volts — 50 min., 30 min„ £4.4.0. 

DPI I RESET TIMERS (illust.). 
240V, 50 cycles, 6sec, 45/-. 




Incorporating 
e or more cams 



s 



PEN RECORDERS 

Elliott Bros. 3-7/8983. A single Pen Recorder. 
5mA complete with Sweep and Recording Unit 
Type II66A. Voltage range 0-5V, 0-I0V, 
0-25 V. £27.10.0. 

Southern Instrument* Two Pen Recorder. 
Complete with Amplifier and 4-specd gearbox, 
£89. 

Kelvin & Hughe* Two Pen Recorder, £89. 
Two pens activated mechanically 
by 6k O S.P.S.T. Relay Deviation 
0-1 in. Chart width l'3in. 

Driven by Synchronour Motor 
Sangamo Weston 57 Motori rev. 
perhr.* £7.10.0, 
* It should be noted a wide range 
of chart speeds can be achieved by the replace- 
ment of the motor. 

Portable Single Pen Racorder by Record 
Electrical (illus.). 3in 

chart, sensitivity 500mA. 
Coil res. l-53kQ. Fully 
interchangeable scars avail- 
able to make a wide range 
of chart speeds. 200/250V. 
Size 8x11 K 6in. Brand 
new, comp. with chart and 
ink. List over £100. OUR » •»= 
PRICE £49.10.0. 

Elliot Portable Single Pen Recorder. 3+in 
chart. Sensitivity 500mA. I and 6in per hr. 
£19.10.0. 



I 



ELECTRONIC BROKERS LTD. 

8 BROADFIELDS AV., EDGWARE 

MIDDLESEX 

TEL: 01-958 9842 



S.B.-Superb Bargains Every Month 

The greatest High Fidelity Bargains ever offered 

STEREO AMPLIFIER. I3£ gns, only. Retail value 27 gns, A Fully Transistorized High Fidelity Stereo Amplifier complete in free standing case. 
Switched input facilities. Socket II) tape or crystal P.V. (2) radio tuner, (3) ceramic P.U.-mike. Controls: Volume, Bass, Treble, Balance, Input 
Selector Switch, Stereo/Mono Switch, Facia plate rigid perspex with black/silver background and matching knobs. 

Output 6 watts per channel (R.M.S.) 12 watts Mono, Free response to 3dB, 20 -20.000c 's bass boost approx. 10 HdB. Treble out 2-l6dB 
approx. Negative feedback — ISdB over main amp, 

12 months' unconditional guarantee. P./P. 6 .-. 



• BARGAIN — High Fidelity Stereo Amplifier. Our Price 7 gns. only. 
Retail value 16 gns. Complete in free standing case. Ideal for crystal or 
ceramic P.O., Tape, Radio, Tuner, Fully integrated. Rigid perspex facia 
plate black/silver matching knobs. 

Output 4 watt* per channel R.M.S. 12 months' unconditional 
guarantee. P.P. 5/4. 

• BARGAIN — High Fidelity Mono Amplifier. Our price 7 gnt, only. 
Retail value 14 gns. Providing excellent results at all output levels and 
complete in free standing case. Frequency response: 30 20,000c , s 
2dB. Sensitivity: 5m V (max.). Harmonic distortion: 0-5% at 1 ,000c, s. 
Output: 3—8— I S ohms. Input: Mike, Gram, Radio, Tuner, Tape Recorder. 
Input selector: facia rigid perspex black/silver with matching knobs. 
Output 6 watts R.M.S. (certified). 12 months' unconditional 
guarantee, P./P. 5/6. 

• BARGAIN CHANGER DECKS AT LOWEST PRICES EVER 



Garrard 


1 .000- 1 ,025 


£6.5.0 


P./P. 7/6 






2,000-2.025 


£6.15.0 


P./P. 7/6 






3,000-3,500 


£8.19.6 


P./P. 7/6 






AT/60 Mk II 


£12.10.0 


P./P. 8/6 






SP25 Mk. II 


£10.15.0 


P./P. 8/6 






LAB80 Mk. 11 


£23.10.0 


P./P. 10/6 






SRP22 


£4.10.0 


P./P. 5/6 


8.S 


R. 


UA'75 


£6.5.0 


P./P. 7/6 



Plinths to suit all the above. Beautifully styled and first grade manu- 
facture, £2.5.0. P./P, 5/-, 

• BARGAIN A superb Mains Tuner. Our price 6 gns. only. 

Retail value 12 gns, A.M. superhec transistor unit with own ferrite 
aerial. Simply add to any of our amplifiers for outstanding results, 
12 months' unconditional guarantee. P.'P. 5/6. 

• BARGAIN- F.M. Mains Operated Toner. Our price 8 gns. only — 
16 gns. value. 6 transistor S/'M horizontal dial, 2 I.F. stages, coupled 
double tuned discriminator terminating in l.F. Ample output for all 
amplifiers. 

12 months' unconditional guarantee. P./P. 5/6. 

• BARGAIN- L.W.-A.M. F.M., Mains Operated Tuner. Our price 
16 gns, only. Retail value 30 gns. Fully transistorised. Output 5mV 
exceptional sensitivity and selectivity on all bands. L.W. 180 360RC/S, 
A.M. 600-1, 400kc/s, F.M. 88IQ8Mc/s. This unit is complete with aerials, 
three-band horizontal dial. 

12 months' unconditional guarantee. P./P. 6/6. 

• BARGAIN - Record Player Amplifiers. 47/6 only. EL84 output. 
two controls, flying panel, a.c. mains operated. 230-240V. Now inc. 
chassis, fully built and tested. 

12 months' unconditional guarantee, P./P. 2/6. 

• BARGAIN -Record Player Amplifier Unit. 52/6 only. Complete 
with valves (UCL 82) output. Fully built and tested, mounted on board 
with Sin round speaker. Knobs supplied, all leads attached ready for 
instant connection to your turntable. 

12 months' unconditional guarantee. P./P. 3/6. 

• BARGAIN — Record Player Cabinets. Our price 52/6 only. 
Retail value 4 gns. Strongly built wooden frame, two-tone gilt fittings, 
carrying handle, suitable for any amplifier, ample space for speaker. 
Matching Garrard or B.S.R. cut out board supplied free of charge. 
P./P. 5/-. 

• BARGAIN Speakers- -Standard, Sin round, 7 X 4in elliptical, 
8tn round, all 3 ohms. Our price 15/-. P./P. 2/6. 



• BARGAIN Speaker*, Hi-fi E.M.I. 8 Sin elliptical, 12,000 lines 
gauss. Alcomay magnet, rating 5 watts, 3 or IS ohms. Sold elsewhere at 
SO/-. Our price 27/6. 

• BARGAIN Speakers, Hi-fi- E.M.I. 13 Sin elliptical, 13,000 lines 
gauss, Alcomay magnet, rating 10 watts. 3 or IS ohms. Sold elsewhere 
at £4.0,0, Our price 47/6, 

Brand new, 12 months' unconditional guarantee, P./P. free. 

• BARGAIN Speakers. Hi-Fi - The Baker Selhurtt De-Luxe 
Stalwart, 12in round, 15 watt rating. 12,000 lines gauss, 3 or 15 ohms, 
response 45 13,000c/s, Bass resonance 40-S0c/s, solid aluminium chassis. 
Our price £4,19.6. 

Brand new, 12 months' unconditional guarantee. P./P. 6/6. 

• BARGAIN Speakers, Hi-Fi -The Baker Selhurst Guitar 
Group 25, 12in round, 25 watt rating. 12,000 lines gauss, 15 ohms, 
response 30 lO.OOOc/s, solid aluminium chassis, heavy duty cone. Our 
price £4.19.6. 

Brand new, 12 months' unconditional guarantee. P./P. 6/6. 

Cartridge* All Bargain Prices 

Sonotone— 9TA/H.C. Sapphire (Stereo) £2.0.0 
Sonotone 9TA/H.C. Diamond (Stereo) £2.S.O 
Sonotone 2T/Ce ramie H/C (Mono) £1.2.0 

Acos GP91/3 (Mono) £1.0.0 

E.R. S.M.B. Crystal (Mono) £1.0.0 

E.R. S.M.B. Ceramic (Mono) £1.0.0 

E.R. S.M.B.X. Ceramic (Stereo) £1.5.0 

T.C.8. H. (Mono) £1.0.0 

T.C.B. M. (Mono) £1.0.0 

C.I, Stereo £2.2.0 

All cartridges are supplied with fixing brackets and screws at no extra 

cost. P./P. on alt above 2/6. 

• BARGAIN— "Phillips" Intercom System. Our price 59/6 only. 
Retail value £6.6.0. This equipment is ideal for baby alarm, office, home 
and hundreds of other uses. Absolutely brand new in handsome pre- 
sentation case containing all leads, etc. 

12 months' unconditional guarantee. P./P. 3/6. 

• BARGAIN — car radios. Our price 9 gns., retail value 16 gns. 
Negative or positive earth (switched), famous brand name, fully tran- 
sistorized (12V), medium and long waves, chromium escutcheon. Speaker 
and fitting kit supplied at no extra cost. 

12 months' unconditional guarantee. P./P. 7/6. 

• BARGAIN car aerials. Our price 22/6 only, retail value 37/6. 
Heavy chrome plate, retractable. A snip buy while stocks last. Brand 
new in maker's package. 

• BARGAIN Slimline T.V. receivers in mint condition. 17, 19, 
2 1 in, checked complete and working but less l.F, strip. Our price 
£9,10.0 only. l.F. strips supplied at 45/- if required. Fitting charge (or 
l.F. strip if requested £2.2.0. P./P. T.V. set 30/-. P./P. l.F. strip S/-, 
If purchased together 30/-. Personal collection advised otherwise 
despatch at customer's risk. 

• BARGAIN Car Radio Portable. Our price 4j gns. only, retail 
value 7i gns. Single wave band (medium), fully transistorized, ideal for 
home or car. A beautiful radio, the performance has to be heard to be 
believed. 

12 months' guarantee, P./P. 4/6. 
Free with this radio, suitable window mounting car aerial. 

• BARGAIN Diodes, Our price £1.0.0 for 750 in 750 lots only — 
assorted. 



OUR HIGH FIDELITY EQUIPMENT IS NOT ADVERTISED DUE TO SPACE LIMITATIONS. 
FAMOUS BRAND NAMES -LEAK, WHARFEDALE, ROGERS, THORENS, RADON, WYE. 

UP TO 15% DISCOUNT AGAINST RECOMMENDED RETAIL PRICE 



IN STOCK ALL 



S. B. ELECTRONICS 



BOLTON 25881 



ATLAS HOUSE 

CHORLEY OLD ROAD 
BOLTON 

LANCS 



.189 



true to specification 





• Silt 9* in x 9iin x 4 i in deep plus detachable base. • 15 ohms Impedance 

• Up to 14 watts loading, a) Smooth response between 60 and 16,000Hz 
British manufacture 



Q.14 COMPACT 
HIGH-FIDELITY LOUDSPEAKER 



When Sinclair Radionics decided to design and 
manufacture a new loudspeaker, it was required 
from the start that its performance should be worthy 
of today's best high fidelity standards and be so 
reasonably priced that the greatest numbers could 
afford it. By using ultra-low resonant materials to 
form its acoustically contoured housing, outstand- 
ingly brilliant performance resulted. Furthermore, 
the unusual form of the Q.14 meant it could be used 
as a free-standing shelf speaker, as a wall-corner 
sound radiator or flush mounted singly or in multiple 
units on a flat surface such as a wall The correctness 
of the design of the Q.14 has amply proven itself 
since within a few months of its introduction, it is 
already amongst the four most demanded loud- 
speakers irrespective of price. Independent labora- 
tory tests have already shown that the Q.14 has 
amazingly good performance characteristics. As a 
judge of good sound yourself, your ear will confirm 
this instantly. At its price, there is nothing to stop you 
changing to Sinclair at once. 

The Q.14 is finished in matt black with solid aluminium 
bar embellishment on the front. Supplied in strong 
fitted carton and sent post free under money back 
guarantee if you are not satisfied. 




£7.19.6 

IDEAL FOR ZJ2 MONO AND STEREO SYSTEMS 



SINCLAIR RADIONICS LTD., 22 Newmarket Road, 
Cambridge Phone OCA-352996 



390 




COMBINED 12 WATT 
AMPLIFIER AND PRE-AMP 



Built, tested 

and 

guaranteed. 

89/6 




No constructor's transistor amplifier has ever achieved such success as 
the Sinclair Z.12, It favours the user in so many ways — with fantastic 
power-to-size ratio, with far greater adaptability, with freedom to operate 
it from batteries or mains power supply unit (the new PZ.4 is ideal for this) 
and with the opportunity to obtain superb stereo reproduction for very little 
outlay. Countless thousands of 2,1 2s are in use throughout the world in 
hi-fi Installations, electronic guitars and organs, P. A. installations, inter- 
com, systems, etc. This true 12-watt amplifier is supplied ready built, 
tested and guaranteed together with the Z.12 manual which details a 
number of control circuits enabling you to match the Z.12 to your precise 
requirements. For complete listening satisfaction, use your Z.12 system 
with 0,14 loudspeakers, tt assures superb quality with substantial savings. 



SINCLAIR PZ.4 STABILISED MAINS POWER UNIT 



A heavy duty stabilised power supply unit of advan- 
ced design developed specially for systems using 
cne or more Z.I 2s. For running from standard 
A.C, Mains supplies, the PZ.4 delivers I8V, D.C. 
at I.SA. Supplied built, tested and guaranteed. 



99/6 





SINCLAIR STEREO 25 

• Input switch in/Treble /Bass/ Vol- 
ume/Balance Controls 

• Sensitivity for 10 watts into 1 .5 
ohms per channel 

Mic. — 2mV into 50K ohms 
P.V. — 3m V into 50 K ohms 
Radio — 20m V into 4.7 K ohms 

• Equalisation correct to within 
±- I dB, RIA A curve, 50-20,000 Hz. 

• 6JX2JX2; ins. plus knobs. Alu- 
minium front, fjfl 1Q 6 
Ready built and tested. Lu.13.0 



No increase in price 

rful rec< 
pu^cias* 
inHrie ( 

eWieh yi 



Prices Tor this fantastically tiny, powerful receiver 
remain the same in spite of increased pur^ase tax 
so thatthe Sinclair miercmacic is noeonjBie most 
original and efficient set of its kind eve J^pduced, 
it is the best value too. Aseasy tc tskeWth you as 
your wrist watch. Includes superb magnetic ear- 
piece, tunes over M.W, and plays anywhere. 



i 



Complete kit i>[ 1 ft. f ft Reads built 

parts inc. carpicc, , n U/ It with c;if piece 
case, aluminium lf3 | | tested and 
I root panel, CU-. guaranteed. 

Malkwy Mercury fell (2 required) each 2/8. 



596 



YOUR SINCLAIR 
GUARANTEE 

Should you not be completely 
satisfied with your purchase when 
you receive it from us, your money 
will be refunded in full at once and 
without question. 

PULL SERVICE FACILITIES 

AVAILABLE TO ALL 

SINCLAIR CUSTOMERS 



To: SINCLAIR RADIONICS LTD 
Please send POST FREE 



22 NEWMARKET ROAD, CAMBRIDGE 




391 





Kew 7 Midget Multi Taster. Eagle's new super 
midget tester operates on the same principles and 
provides the same performance as larger meters*. - 
with the same degree of accuracy. New 1 unitized 
construction makes the Kew 7 one of the world's 
smallest pocket multimeters — about the size of a 
cigarette packet. Mirror scale* "turn around" test 
leads, battery compartment, printed circuit* voltage, 
current, and resistance measuring ranges qualify this 
instrument as a versatile, handy toe) that experi- 
menters* Students and servicemen will always want to 
carry with them. Visit your Eagle dealer to inspect 
this exciting new midget meter , . . such good value 
at 59/6d* 

FOR VERSATILITY, RELIABILITY AMD SOU MD V ALUl 
INSIST ON 



^i# 




Distributed by B. Adler & Sons (Radio) Ltd., Coptic Street, London, W.C.I 



£»rMfi*K 



LONDON'S LOWEST PRICES! 



Yaliei 

IA7 9;8 

1AD4 18/6 

1AJ4 7/8 



IBs 
1C3 

1D6 

idi:i 

1F2 

1FD1 

l€-t 

l Hi 

1LAU 

1LM4 

1M3 



9/8 
9/8 
9j- 
5; 8 
6(6 
7/9 
10/- 
8/6 
8/- 

K- 

9,8 



1X21B 8/- 

1N25 18/8 

IK 38 A K- 
1X72 

ipii 



IRS 

1S4 

1T5 

2 A 3 

«! 

2C2B 

2C61 

2D2 

2D21 

3A3 

3A8 

3C4 

334 



lif. 



4/6 
8/3 
8/8 
87- 
7/8 
71- 
10/- 
II- 
10/- 
71- 
1B.-B 
14/- 
10/- 
9/6 
67- 



10/8 
10/- 
10,'- 
10/8 
14,- 



(1AB4 

0AC5 

IJAFH 

HAG 7 

6AJT 

BAKU 

6AL3 

■iAM.i 

BAQ4 12/ 

(IAQ8 

8AR0 

HAS 



12 5 

13 S 
8 6 
6.8 
5/- 

10,6 
5 8 



8/- 
17H 



6AU5 25/- 

0AV5 13/- 

6 AX 4 10/- 

iJBDT 9/6 



BBF7 

UBJi 

obk; 



14/8 
22/6 
11, 



6 8MB 10/ 
■ ili> i, 9,,'S 

ubq: 

HBR 

iBW 



10/ 
12/6 
12 '6 
BBYfl 12/6 



JBXT 

6C« 

BC10 

6C31 

6CBC 

6CFS 

6CJ6 

6CK6 

BCM5 10/8 

6CQ5 6/- 

ecve 13/- 

6CW4 14/6 

6CYB 9/- 



12 - 
8/- 
11/- 
13,8 
8/6 

e/6 

11/8 
B/B 



6D3 
6D8 
6D18 

ii.D7... 
6DS8 

(iE.'r 

BEJ7 

BET 6 

6F6 

6F8 

BF13 

0F16 

BF19 

(iF22 

0F20 

UF30 

itgttd 

liGti 

BGV8 

OHO 



i;Lf; 

E&lfl 



9/- 

12/6 
11/8 
9/- 
S/6 
10/- 
9 8 
12,- 
10/- 
71- 
8/8 

11.5 

7/8 
9/6 

7/6 
9/6 

10/6 
3/8 

12/6 

e/- 



10/- 

8,<- 

ao;- 

12/8 
8/6 



6LD3 10/6 
6 LI 120 7- 
67- 



tiPl 

oeis 

6Q4 
0R7 
687 
09 D7 

est; 7 

HSK7 

6SQ.7 

6ST7 

615 

BV4 

6X3 

BYB 

7A4 



7DJH 

7E7 

7Fli; 



18/- 
5,6 

30/- 
3 

12/- 
71- 
8/'- 
8/- 
9/6 
6/- 

10/- 
6,6 
9/6 

13/6 

10 
8/- 
87- 

18/- 

10/- 
8/6 
8 

14/- 

12/- 

11/8 
•/- 

12/- 

14/- 



8/8 

17/6 

12/6 

9.8 

9/6 

6/6 

11/- 

0/6 

9 



7E7 
7W7 
7Z4 
SDH 
9 AS 
9AQ? 
9D4 
'JU8 
10F1 
10FIS 
i'Jl.14 
1 OLD 13 8/6 

10PM 18/- 

12A5 12/- 

12 ACS 10,' 8 

12 A Eli 8:8 

12ALS 9/- 

J2AT7 S/8 

12AVU 7/6 

12AW7 22/8 

12BAU 8- 

12BLS 10/- 

12DT7 8/8 

12FB5 12/8 

12J7 9/- 

12KT 9;- 

1237 11/- 

12SFE 11/- 

128H7 71- 

I2SL7 9/8 

I2SR7 7/- 

12SY7 8,'- 

12Y4 4,6 

13D3 7/- 

13GCS 18/8 

14EU Sl- 

14L7 6 6 
14S7 

lilM 

16B 

16Y9 

17Z3A 

18DB 

19BX6 10/8 

19DC8 9/- 

10G6 

I860 

19Y3 

20P1 

WUl'i 

21B0 

26C6 



12- 
10/- 

16/8 
7/6 

7 8 



17/8 
7/8 
7.'6 

14/- 

21/6 
9'6 

12f- 
28F(;6 1S;- 
20Y5 12/- 
2SZ6 18/- 
23AKS 8/6 
3(1 AS 9/- 
30C15 15(- 
30F5 13/6 
30FL13 12/6 
30L15 14/6 
30ri2 15,- 
30P1S IB— 
30FL14 1S 



3SA3 

3BC5 

36 W 4 

30 ?.& 

4IA 

42MP 

4SBU 



11/- 
8,6 

0'8 
8 8 

a 



.-■IKl" 12/6 

62TH 11/- 

(I3TP 8/8 

flflMK 8/6 



141DDT 8.8 
1S0B2 18,- 
177 6/- 

277 6/ - 

12,6 
6.- 
6 6 
10/8 
3/8 
6/6 
10/6 
71- 
12/6 



40«A 

879 

1221 

[■274 
1638 
1853 
2101 
6488 
38807 



A4051 12/6 
ACS 9/6 

At! 52 II 8/8 
ARP34 9"8 



Vi:4 
AZJ] 

AZ4I 

BB3 

B1D2 

B32S- 

B7iy 

BF6-2 



8/8 

10'- 
8/6 
6/6 
5/6 
8,6 
8/6 

11/- 



JJAF4 L 12/8 
DAFBti 7/8 
DF92 4/- 
DH77 8/6 
DH11H 8/8 
DHI47 8/8 
DH7J8 10/- 
DK92 11/- 
DL91 8/- 
DL94 8/8 
DNI43 13/8 
E A scan B/8 
EB34 2/6 
EBL'41 10 6 
EBC'Ji 7f- 
EBF8U B/6 
FCC40 12/- 
Et!C83 8/6 
ECC86 8; 6 
ECC1SU14/- 
ECF80 8/ 8 
ECFH6 12,8 
ECH81 8/8 
ECL8U 8/8 
ECLS4 13/6 
EF37A 10/8 
EF41 11/6 



KFS;» 
EFSSi 
EF95 
EL33 
KLSfl 
EL8 1 
ELt'O 



12.8 
7/6 
7/6 

12/6 

£7/6 
12,6 
8/- 



ELLSO 17/ 
EMS0 8.8 
EN83 IB/8 
EY8« 8/8 
EZ4W B/8 
EZH1 6/6 
HBCUU 6,6 
1162 12/6 
HPfi 8/- 
KT61 20/- 
KT88 27/6 
1A'119 10/6 
LN319 161- 
LZ339 16/- 
N19 



S/8 
10/6 

20/- 
11/- 
9/- 
8/- 
86 
8/- 
18/- 
13/- 
9/6 



Ml 42 
K147 

NISI 
N1S4 
N30H 
NSTf' 
\727 
PCSH 
' PCS" 
PC95 
FC97 
PC900 14/- 
PCC84 8/8 
PCCSE 8/8 

FCCRB 14/- 

PCCS'J 14/6 
PCC18914/- 
PCCS05 14,6 
PCC806 18/- 
PCE80014/6 
PCF80 12/8 
PCF82 9.' 6 
FCFS4 10 6 
PCF80 11/- 
PCF87 15'- 
PCF800 167- 
PCFS01 12-6 
PCFS02 12:6 
PCF806 12/6 
PCF808 15/- 



PCF808 15. ■ 

[Ti.-i 14 8 

Pt'L8:» 10,8 
PCX83 10/- 
FCL84 10/- 
FCL85 11/8 
PCL8B 11/6 
PCL8B 15,'- 
FCL800 15/- 
1't'LSOl 15/- 
PFL20O16/8 
PL3U 12/6 



Pt86 

PLH] 
PL32 
PLK3 
PL84 



17/6 
9/6 

9/- 
9/- 
8 8 



PL3W2 116 
1'LaOU 16/6 

ri,-'i. 15'- 
PY32 11/6 
FY 33 11 .'8 
PY84J 
FYS I 
FY 82 
PY8.1 
PY8B 
PY30 1 



7/8 
7/8 
7/8 
9/8 
18/8 
PY800 10/6 
IVbUl 10/6 
PZ30 11/8 



B1H 
R12J 
I"2i: 
l'4H 
l!54 
1 7« 



10/6 
10/6 

12 a 

12/8 
14/- 



l : 2!U 
1/3 1 9 
T34W 



7,6 
10/8 
10/8 
7/8 
10/6 
I'ABCsuS/e 
rii-u 13 8 
1TBF80 9/6 
U09B 8'6 
VCOfUt 147- 
VCHhl 8 P - 
T,"F41 13/6 



ITKSfl 
l'L4l 
VLfJ 
Ct*12 
UY85 
W118 
W145 
W149 
W727 



lo c; 

L0 ; 8 
9 6 

e I 

8« 

12 
12- 

6 - 

7 8 



WD 150 11 - 

X18 11/- 

X81M 

X143 

X1G0 

K14:. 



Z719 7/6 
ZD1G2 9,8 

Semico aduc- 
ton-TrRMii. 
tan, Diodes 

1N21 B 5/- 
1N34A 2/- 
1K91 5f- 
1N25B 7/6 
IN43S 5/- 
1K703A 3/6 
IS 1329 5/- 
1N3075 3 6 
1S111 4/- 
1S131 4/3 
1R401 8/- 
18420R 12/6 
187075 4/6 
2G301 91- 
2G306 7/6 
2G371 4/6 
2G401 El- 
2(i414 5/- 
2G417 4/8 
2N257 10/6 
2N'3S8A 9/6 
2N0B5 12/6 
2X598 7/6 
2N697 7/6 
2N70M 4:6 
2X865 7/8 
2X 1091 9/8 
2X1304 6/- 
2X1307 7/6 
2X1132 12/6 
2X1755 15/- 
2X210012/8 
2X2398 29/6 



2X28L.4 8/8 
2X3412 7/8 
2X3528 12/6 
2X3707 7/8 

2X38 1 9 12/- 
2H002 10/8 



28005 
28013 

2S01K 
2H30 I 
28322 



15 
20/- 
17/8 
12/3 

7/8 
19 6 



6' 

m 

2 8 

( 8 
8'8 
8 8 
5 - 
4 8 
8 - 
15/- 
8/8 
6/- 



2S321U 10/- 
25H2C) 88/- 
W0AS 6/8 
4 00/ 1-21 
000/5 
AAZ13 
AG 120 
AC 128 
AUY17 
ACY20 
AOY2H 
AD1B1 
AEY1I 
AFH4 
AF117 
AP125 B'B 
AF13i' 10- 
AF230 12/8 
AEZ12 10/- 
A8Y83 6/- 
ASZ21 12/8 
AU101 30,'- 
BL'107 6/- 
Bt:Y10 7/6 
B<:Y:i3 7/8 
Bi'Y3H 12/8 
BFY17 7/8 
BFY52 8/8 
B8Y56 4/- 
B8Y51 7/8 
BMY96A 4/8 
BY 100 4/6 
BYZll 10/6 
RYZ15 20,'- 
C:R81/20 
I2SF102) 
200P.1.V 
1 "lltll' 
ThyrisUir 
9/8 
CRK3/20 
200F.L.V. 
3 amp 
ThvrlHtur 
10/- 
t:K707 8/- 
CV2919 8/- 
CV222B 20,- 
(.'W12E £,- 
DD0O:i 3/6 
DK14 8/- 
F8T1/1 3/- 
GET10/-K- 
GET 102 6/- 
GET114 4/- 
CET571 8/- 
GET875 91- 
GET883 8/- 
GETS90 78 
(IEX54 88 
GEX951 6/- 
C(J6M 4/6 
HG1078 2/- 
H81012 8/6 
JK10B 15/- 
JK20A 17/8 
M3 1/6 

MAT 120 7/9 
XKT2116'- 
XKT214 4- 
XKT218 8/ - 
N KT223 8/ ■ 



NKT225 3/6 
XKT22S 6/- 
XKT265 8/6 
XKT273 4/- 
XKTi;77 5/- 
XKT304 8/- 
XKT077S/- 
XKT777 8.- 
MPF103 9/9 



3/- 

3/- 

2/- 

21- 

2 

8/8 

7/6 



OA5 
OA10 
OA70 
OAJtl 
OAWO 
OA9U 
OA210 
OAZ204 8/6 
OAZ207 8/8 
OAZ210 6.r6 
OAZ213 6/6 
OAZ242 4/6 
OAZ247 4/6 
OAZ291 9/6 
OG1U 7/6 



OC23 

OC2U 
OC35 
OC42 



12/B 
91- 
10/- 

s/- 



OC44M 5/6 



5/8 
17/6 



OC4B 
OC68 
OC71 
OU75 8- 
OC73 S,'- 
OG811) 8(- 
OC81Z 6/- 
GL'83 S/- 
GC123 12/6 
OL'UI 18/6 
OCI71 6/- 
OC203 10/8 
OC20U 17/8 
OR PI 2 8/6 
RS34BF 9/- 
SCR71 15/- 
8T141I 4/- 
SVG) 15/- 
SX62 8/8 
8X042 3/6 
8X646 16/- 
SZB0A 7;"6 

7/6 



TK20 
TK25 
TK3ii 
TK41 



6/- 
91- 
4/- 
4/8 



VA1010 


It- 


VA1027 


2 S 


YA lOlili 


2 - 


VR35 


6 B 


Y Ki.il 


8.8 


Y405A 


12,8 


XA111 


2 - 


XA103 


a - 


XA141 


3- 


XA1B1 


3- 


XA102 


5- 


XA701 


5- 


XD202 


W- 


XB113 


M 6 


XCI01/ 


3 - 


XG183 


5:- 


XG142 


9 '6 


XS101 


i ■■- 


XU004 


4 8 


ZB4-3 


4 8 


ZB22 


4 6 


ZFlo 


4,6 


ZE11 


71- 


ZK31 


25 - 


ZS72 


7,6 


ZT45 


8 8 




SIB LIND-AIR OPPOSITB 



392 



LIN ED-AIR 

(OPTRONICS) LTD. 




25 & 53 TOTTENHAM COURT ROAD, LONDON, W.1. tw. oi-sso 453417679 



Open 9-6 D,m. Monday to Saturday inclusive. Open Thursday until 7 p.m. 



GARRARD DECKS 






FAKE 122/17 

12ln!n2*WATT 
HEAVY DUTY 
HI-FI 
LOCD 
SPEAK- 
ERS .With 
high effl- 
c 1 e n c v 
Antistropk: 
r'crrl te magnet . 
17,000 gauss, Imp. 3-5 ohms. Brand Mir 
anil guaranteed. List Price til. LIHD- 
AIR PRICE £8.19.6. V. * P. 7 6. 



E.M.I. COMBINATI0K 
LOUD SPEAKERS. 13i 
* 8,in. Elliptical with 
3(in dla. Tweeter. Imp. 
H ohms. Power handling 
10 watts. Brand new and 
guaranteed. L ist price 
JtS.5.0. LIMD-AIR 

PRICE 99/6. P. * P. 7/6. 
(Also available without 
tweeter 89.,' 8. P. * P. 
7/6.) 



PAKE 301 

3 In 
TWEETER a 
Imp. 3-5 ohms. 17,000 
gatiBB. 12 watt. Brand new 
and guaranteed. List price 
£3.15 0- LtND-AIR PRICE 589. P. * I". 8/8, 

GOODMANS SPEAKER BARGAINS : 

Sin 3 ohms, 15 6: Gin 3 ohm, 28,6; Bta 
3 ohm, 32/8; lOln 5 ohm, 65,'-: !0in x fiin 
3 ohm, 32/8, Tweeter, 19:8, 1*. .V P. 3/6 
per Speaker. 



STEREO HEADPHONES 



Enjoy Stereo Sound as 
von have never heard it 
before, MODEL TTC. 
01111 as Illustrated, 
Woft padded earphones. 
A ill ust at 1 1 e headband. 
Impedance £ ohms per 
phone. Freijuenev range 
2S-13.000e/s. With ott- 
lead. Price 89/8. P. ft P. 
4/6. Other similar tlBM 
available. AKAI ASE8S. 
n ohms. 19.9.0. CORAL 
£102 10 ohms, £5.19.6. 
EAGLE SEL 16 ohms. 79 6. T.T.C. Stetho- 
scope 8 ohm-., 49/8. P. * P. 4/6 each. 




Input 0-2O0, 220, 240V 
Output 110%'. 
TOW £1,7.8 
TOW £1,17.0 
100W £2.5, 
150W £2.16.0 
200W £3.8.0 
300W £4.5.0 
400W £4.19.8 
MKVW £5.9.8 
900W £9.9,9 
Post extra 



1, 000 W £9,9.0 
I.500W £15.15,0 
'-\0O0W £18,10.0 
3,0001V £35.10,0 
4.000W £34.19.0 
0'30V, 1A 80/- 
30 V, 1A 17.8 
030V, 2A 37 8 
30V, 3 A 48- 



!WH 



Input 200,260% 60c s. 

24V 3 A £2.12.8 24V * A £5.5.0 

24%' 5 A £3.15.0 24 V ISA £8.15.0 

Post extra. 

Mains and Out put transfarmer lists available 

on request . 



EXTENSION 
TELEPHONES 

ONLY 

87/8 P. * P. Hi-- 

Complete with lead, automatic dial numbered 

1-10 and internal bell. Guaranteed ]*rfeet 

working order. Made by famous manufac- 
turer to CI. P.O. Speeitieati'm. 



Sit OPPOSITE 




3000 with Suuutoiie MTAHC Klerco Cartridge , 
3000 with Sonotonc BTAHC Diamond Stereo 



TEAK FINISH 

PLINTHS with i>crspe>. 
cover 61 ens. (fur LA BWI 
*J gns.). P. A: P. 12/6 
Agents for Thorrn-, Dual. 
Goldring, etc. 



Cartridge 
VT60 MKI1 less cartridge 
CTiJO MK1I with Decca Derail. 
J*P. 25 MKII less cartridge 
SP:25 MKII with Deceit JDeinn 
A P. 7S less cartridge 
LA n."0 MK'1 1 less cartridge 
All plus |\ 

MOM Curt liilKv 17,'»>cstra. 
Stereo Cartridge 22 est™. 



stereo 
BtCMO 



Cartridge 
Cartridge 



£9.18.9 

£10.19.6 
£13.19.6 
£18.14.8 
£11,19.8 
£18.14.0 
£24.3.11 
£24.19.0 




An ideal basis for building jour uwn port- 
able record player. Jusi add speaker and 
turntable, and you will have an above- 
nverage model for a mere fraction of the 
cost. 2-3 watt printed circuit with 
control pniiel on flying lead. ON, OFF, 
TONE CONTROL AND VOLUME. 
colourful escutcheon. Brlmnr valves: 
EZSO, KCL82 and composite Inslallat 
booklet. Price OC/ P. * P. 3/6 



85/- 



BARGAINX»FFER ! FANTAVOX CASSETTE TAPE PLAYER 



Specially designed to replay the well known and 
popular MusicassetlcH prerecorded (ape cassette 
offering ■ wide choice of all types of music from pop 
to classical, t p to 40 minutes id quality repro- 
duction through built-in speaker, sluiplr oft play 
and vol nine controls . Fit 1 1 y t ra us i st or iscd opera i i r i s 
on six penlight batteries. Modem compact Btylitig 
with earpiece wiokrl and wrist alrap. Size 8] 

hntkvirphice. £9.19.6. %£$?-■*" 





ft Transistor KM tuner. Eiwjueney range M- 
lOSMc's. J«ijc B 4 21 in. Ready built tor 
use with most amplifiers. V battery opera lion. 
Complete with instruction*. LIST PRICK '■> t*». 

LIND-A1K PR ICE f gUS. P. A P. 4 



MULTIPLEX ADAPTOR 

for above for Stereo Radio 

Recaption £5.19.6 extra 




controls, £8.19,9. O 



UNEAR AMPLIFIERS 



Latest b.c. Mains Models ofleiing highest qnallt* 
at modest cost. 

LT99. All Transistor 12 watts .Stereo. Inputs for 
Tuner, Oram, Mike, Separate Bass, Treble, 
Balance and Volume Controls £15.15,0, Carr. 7 '6. 
Teak case £3.10.0 eilrn. 

PTA 15 (as illus.). All Transistor. 15 watts Mono. 
Inputs lor Tuner, firam, Mike, (mitar, Bass, Treble 
and two volume controls, £16.16,0. Carr. 7/6. Teak 
case £3,10.0 extra, LT45, 2 Valve 6 watts Mono. 
Inputs fur Tuner, Oram. Bass, Treble and volume 
Metal cover In'- extra. Foil details sent <>u request. 



9 in t ELECTRONIC KIT 




Build in in different projects from one 
basic kit— simple instructions, no tech- 
nical knowledge required for you to build 
a Folke Siren, Metronome. Morse Code 
amplifier. Electronic Massncer, \V(T 
Transmitter, Radio Telephone, One- 
transistor Radio Two-transistor Radio, 
Electronic Music Kit. Completely sftle- 
operated on 9V PP3 battery. Hours ol 
fun for boys and dads of all ages. Complete 
with all parts and simple step by step 
instructions ONLY 89'8. P. K P. 5 -. 



MODEL TTC. 1001. 
20,000 O.T.V. with 
overload protection : 
■ I.e. volts, 6, 2o, 125. 
500, 2.500V: a.e, 
volts, JO, 50. 250, 
100V: d.c. mA 
250mA-50A. With 
prods and carrying 
case. OSLY " 



85/- 



P. & P. 3-6. 



MODEL TTC. 
1030. 50,000 
O.P.V.; d.c. 
volts, 0-3, 12, 
60, 120. 300, 
600, 1.200V: 
a.c- volts, 1, 30, 
120, 600. 

1,200 V: d.c. 
mA 03-300. 
With prods 
and carrvinc 
case ONLY 
£11.19.9. I". -\ 




ALL POST 
ORDERS TO 
Dept. P.E.668 
25 Tottenham 
Court Road 
London, W.1 



MOTOd 

HAHGAINS 




Ideal (or model 

makers, record 

players, tape 
decks, etc, 

6.3 d.c. Motor. 
10,000 r.p.ui. at 
230mA. l,m » 
Hii dla. Shalt liu 
long ■ 3/64in dla, 
»;6. P. * P. 2/6. 

9V d.o. Oram deck 
replacement motor, 
2in .' liin dia. 
Shalt, Jin long :: 
3/32in. 17 8. P. * P. 
2,'-. 



SYNCHRONOUS CLOCK 
MOTORS 




**catrni (or 40 revw- 
hiLkm« jior hour, 
230v m <$de, with 

I'd -Mill :ni; iiaDgC0. 

size appTo^iniiitely 
l.in ilccji x 2 tin 

A I*. J"! 



SELECTOR DRIVE 



np|rlfCftltottB 

K I e c t r o • 

iri.'lgiicl Ulld 

biWB tixith 
whccL A 

H^Titch MiitdT 

. ■ 1 1 1. 1 contnetfl 
-Tfo coupled to 
this anil 

nirraLiged In 
i ■■ on fur 10 
jmlfes audi &ft 
tvx IS. An 
Auxiliary eMttad \p uurinsiJJv on but ult 
1 in ewty 25. tkmipktc with auppreHSOT, 
r'^ieitvirff^ i»his >;f:rie« rontarl for ratttiBHOM 
f-licr- r iti"ii. J «1*-:t I « Endow -JifljihivFf, s^iK-hhiK 
himps* mnfi^lj", rtf- VI V nr 24V -1 a: tiran-f 
nrvi rkiwl Nnscl. IB'9, T 1 . H K 2'«. 

i H,P. MAINS MOTOR 




Made liv Croiopton Parkinson. Single phase 
I h.r. Motor. 2 30/250 V, 60 cedes. 1-3 amps. 
1,125 r.p.ui. Continuous rating. Spindle 
li x Mil dia. Overall size less spindle approx. 
K x 6in. Perfect condition. A bargain for the 
work bench. 01ILT 78/8. Carr. 20/-. ti h.p. 
Slotoralsftaiallaldc. »9/e.Carr.20--(. 

DELAY ACTION 
TIME SWITCH 

Knits; 
1 rtiuitba, A.c. 
operation 
200 / 2S0V. 
Double pole. 
Will give time 
delays from 
0-10 minutes. 
!4izc 2tin dia, % 
2 tin long inc. 

I in X Sit 6 in dia, spindle. BAK0AIH PRICE 

17,'fj , P. A: P. S 'i- 




393 





VALVES/SEMI-CONDUCTORS 

BRAND NEW & GUARANTEED 






JA2 


•/- 


tiEo 


8/- 


30CIS 14/- 


ECC84 


8/8 


KZ4« 0/0 


FY81 01- 


OBS 


01- 


6J4 


IV- 


30F5 14/- 


ECCSO 


5/6 


EZ41 8/6 


pys2 «/- 


IRS 


8/- 


8J6 


3/S 


3QFL1 16/- 


ECF80 


71- 


EZ8U 5/6 


py83 e/e 


180 


4:6 


6K8 


4/- 


30L15 IS 


ECF82 


7/6 


EZ81 5/6 


PY88 7/8 


IT4 


8/- 


6L6 


9 8 


30P19 14/- 


ECH35 


11/- 


(JZ32 11/6 


PY800 8/- 


IU4 


6/- 


SQ7 


S/3 


30PL1 15/- 


ECH42 


11/- 


UZ34 11/0 


PY801 8/~ 


1U5 


n- 


6SG7 


e/- 


30PI13 16/- 


ECH81 


0/8 


MU14 8/- 


US5 16/- 


2D21 


5/- 


(JSJ7 


7/- 


36L6 8/- 


F,CI1S3 


ere 


PABC80 7/0 


U26 16/- 


3A5 


101- 


6SL7 


w- 


3524 8/0 


ECL80 


7/0 


PCC84 8/6 


U191 14/- 


3Q4 


v- 


6SN7 


5/6 


35W4 5/8 


ECL82 


7/- 


PCC85 8/- 


U281 8/- 


384 


5/- 


6U7 


11- 


SOBS 6,6 


ECL83 


10/6 


pccss ii/e 


USOl 11/- 


SV4 


01- 


6V6 


67- 


50C5 6.6 


ECL80 


»h 


FCC89 11/8 


U801 17/- 


6R4 


w- 


6X4 


4/3 


80 7/- 


EF37A 


01- 


PCC189 lg/6 


UABC80 6/- 


5U4 


a- 


6X5 


5/- 


AZ31 10/- 


EF40 


10/- 


PC86 11/- 


DAF42 10/- 


6V4 


8/B 


7B7 


7/- 


DAF9I 4/0 


EF41 


9/0 


FC8S 11/- 


L'BC41 8/- 


SYS 


5/9 


7C6 


a/B 


UAFOB 7/- 


EF42 


10/fl 


1-C97 8/6 


UBFSO 11- 


524 


8' 


7Y4 


s/a 


DF81 8/- 


EF80 


6/- 


I'Caoi) 0/6 


UBF89 7/- 


6/30L2 


12 S 


10C2 


Iff- 


DF96 7/- 


EF85 


0/6 


PCF80 7/3 


UCC84 10/- 


6AC7 


4/- 


10F1 


8/- 


DK91 8/- 


EF86 


11- 


PCF82 11- 


VUC85 11- 


0A67 


6.1- 


10P13 


16/- 


DK92 8/9 


EF89 


Blt 


PCF84 8/- 


L'CFSO B 8 


fAKo 


57- 


10FI4 


18/- 


DK96 61- 


BF91 


*h 


F<;F86 9/- 


UCH42 10/ ■ 


CAT, J 


8<- 


12AT6 


5/- 


DL92 6/- 


EF92 


il- 


FCF800 15/- 


UCH81 11- 


fiAMC 


4/- 


12AT7 


4/- 


DL94 6/- 


EF183 


7/- 


FCF80110/- 


UCL82 8/- 


6AQ.5 


6/- 


12AU7 


5/- 


DL96 8/- 


EF184 


11- 


PCF802 10/- 


L'CL83 10- 


6AS6 


6/- 


I2AX7 


e/- 


DYS8 6/B 


EL33 


1E ; 8 


PCF805 14/- 


l^F4I 10/- 


SATO 


6/- 


12BA6 


6 9 


B88CC 12 6 


EL34 


11/- 


PCL82 7/6 


UF80 71- 


6AP8 


5 8 


12BE0 


0/3 


EABC80 71- 


KL41 


8/9 


PCL83 O.'fl 


UF8S 7/0 


8BA8 


4/9 


12BH7 


6 6 


E1SOF 15/- 


EL42 


11/- 


PCL84 8/- 


UF89 7/8 


6BE6 


5(3 


12Q7 


5/6 


EAF42 0/0 


EL61 


B/- 


FCL85 9/6 


V1AI 10/- 


UBH6 


87- 


12SQ7 


7/6 


EB91 3/- 


ELS4 


5/- 


1'CLKfi 9/ ■ 


UL84 11- 


8BJ6 


»h 


19AQ5 


6/- 


EBC41 9/8 


EL85 


8/6 


FFL200 lfi/0 


UY41 7/8 


6BR7 


11/- 


20F2 


14/- 


EBC81 7/~ 


EL91 


ih 


PL38 10/8 


UYSS 6'6 


6BZ6 


7- 


■10 Ll 


18f- 


EBFBO 7 6 


EL9S 


5/3 


PL81 7/8 


VR 105/30 


6C4 


3 6 


20 PI 


12/- 


EBFS3 8 - 


EM80 


7/6 


PL82 7/- 


5/6 


see 


*v- 


20P3 


12/- 


EBF89 7/6 


EMS1 


8/- 


PL83 11- 


VE IS 0/305/- 


0CD8 


20/- 


20 P4 


10/- 


ECC40 11/6 


EMS4 


7/0 


PL84 8/8 


MANY 


6CH6 


8/- 


26L8 


6/6 


ECC81 4/- 


EMS7 


7/8 


PL600 14/8 


OTHER 


8CL6 


10/- 


25Z4 


8/- 


ECC82 5/- 


EY51 


7/8 


PV33 0/0 


TYPES IN 


8 


D6 


tl- 


SOCIO 


13/0 


ECC83 6/- 


EY8B 


7/- 


PY80 5/6 


STOCK. 





2N763 4/8 
2N2I60 

14/11 

2N2926 5/- 

AC107 4/0 

AC126 4/0 

ACI27 4/0 

AC128 4/0 

ACY19 6/- 

ACY21 6/- 

AD140 8/6 
AU149 10/- 
ADTI4015;- 

AP1I4 8/6 

AF115 4/6 

AF116 4/6 

AF117 4/6 

AF118 4/8 

AF119 4/6 

ASY28 7/- 

BC107 6'6 

BC108 5/6 



TRANSISTORS 



BC109 5/6 
BSY20 4/6 
BSY2B 4/6 

BSY65 4/8 
BSY95A, 5/- 
GET106 5/8 
GET113 5/6 
OET873 5/6 
OET«74 4/6 
MAT 100 7/9 
MAT 101 8/8 
MAT 120 7/9 
MAT 121 8/6 
OC23 8/6 



OC26 
OC28 
OC35 
OC4I 
OC42 
OC44 
OC45 
OC71 



OC72 
OC73 
OC74 

OC7S 
OC7B 
OC77 

OC78 

tic*: 



OC81M 8/0 

OC81I) 4/- 
OC81DM2/8 
OC82 4/6 
OC83 5/- 
OCI39 0/0 
OC140 11/- 
OC169 4/0 
OC170 4/0 
OC171 4/0 
OC200 9/- 
OC201 11/- 
OC203 IS/8 
ST 140 4/- 



ST141 


1 - 


XA104 


m 


XAJ24 


4/6 


XA125 


m 


XB112 


V- 


XU141 


T- 


PHOTt 




TRANSIS- 


TORS 


12.6 


SIGNAL 


DIODES 


IN34A 


4 ■ 


OA5 


3 6 


OA10 


4B 


OA70 


2.'- 


OA79 


tt- 


OA81 


2- 


OA90 


I 6 


OA95 


a e 



UAZ2001B/- 
OAZ20110/- 
OAZ202 8/6 
OAZ203 8/6 
STC 1 WATT 
2-4 / 2-7 / 3 / 
30 / 33V. 5/ 
Z eerles. AI 
200KW g/8 
7W 5/- each. 



ZENER DIODES 



OAZ208 0/0 
OAZ2Q9 6/6 
OAZ210 6'6 
OAZ211 0/6 



OAZ204 8/6 

OAZ203 8/6 

OAZ206 8/0 

OAZ207 9/0 
SERIES 5% 
3-S / 4-3 / 13 I 10 / 18 / 20 / 

each. 

voltages from 3'9 to 50V. 
each. 1-5"W 4/- each. 



O:\7.-2l-2 0/6 

OAZ213 e/e 

O A 2227 15/- 



PLEASE 

ADD 
POSTAGE 



SILICON 
POWER 
DIODES 



oo p. i.v. 

70 P. I.V. 
150 P.l.V. 
L50 P.l.V. 
200 P.l.V. 
400 P.l.V. 
400 P.l.V. 
400 P.l.V. 
700 P.I.V. 
800 ■P.l.V. 
800 P.l.V. 
1 ,000 P.l.V. 

I, o«o p.i.v. 



290 MA £/- 

lamp 3/6 

lesMA 1/- 

25ii!ii]i 10. - 

Onrop 6/0 

600MA 3/e 

Ocimp 5/6 

Ramp 7/6 
lOOiimp 35/- 

600MA 6/6 

Gamp 7/6 

Oomp 7/B 

BSOMA 0/6 



THYRISTORS 

SILICON 

CONTROL 

RECTIFIERS 

400 P.l.V. 3amp 7/8 

100 P.l.V. 7amp 18/6 

200 P.l.V. Tamp 15/6 

400 P.l.V. Tamp 15/6 




LAFAYETTE TE46 RESISTANCE 
CAPACITY ANALYSER 

2pF-2.000 mfil 
a ohma-200 
megohms. Also 
checks Impe- 
dance, turns 
ratio, insula- 
tion, 200/280 V 
a.e. 

Brm£Bewfl5. 
Carr. 7/6. 



T.E.40 
HIGH SENSITIVITY 
A.C. VOLTMETER 

10 meg. input 10 ranges: 
•01 / -03 / -1 / -3 / 1 / 
3 / 10 / 30 / 100 / 300V. 
R.M.8. 4c/«.-1.2Mc/s. 
Decibels — 40 to — COdB. 
Supplied brand new 
complete with leads and 
Instructions. Operation 
230V a.c. 617.10.0. 
Carr. 5/-. 



T.M.C, 1000 SERIES 
KEY SWITCHES 

Brand New with knobs as 
lollows- 

1 way, 2 c,'o 7/8 ; 1 way, 2 c/o 2b. 7/8 ; 1 way. 
4 c/o. g/-; Sway, 3m., Sm.8/6;2 way. 2c/o„ 

2 c/o. 8/6; 2 way, 2 c/o., 4 c/o. 10/-. 
Post extra . Qtiau 1 1 1 Ses a va liable . 






ARF-100 COMBINED AF-RF 
SIGNAL GENERATOR 

AP. SOIE WAVE 



2 0-2Q0,O0Oc/n. 
Square wave 20- 
30.000 e/a. O/P, 
HIGH IMP. 21V 
P/P 6000 3-SV 
P/F. 

TF. 100kc/8-300 
Mc/m, 

Variable R.F, attenuation lut/est, modula- 
tion. Incorporates dual purpoiie meter to 
monitnr AF. output and % mod, on R.F, 
220/240V a.e. 6X7.10.0, tiirr. 7/0. 

TE-20RF SIGNAL GENERATOR 

Accurate wide nusffVStlgRA] generator cover- 
ing 120Kc/s • 200 
Me/a i in hands. 
.Directly caii- 
bratet). Variable 
E.F. attenuator. 
Operation 200 / 
240V a.c. 
Brand new with 




i t r u c t i o n 
£15,0.0. F. & P 
7/6. S.A.E 
details. 



ftj.- 



AUTO TRANSFORMERS 

0/11 5/230 v. Step up or itep down. 

Fully shrouded. 

500 W. 13,10.0. F. & P. 6/6 
1,000 W. 15.10.0, P. * P. 7/6 
1,500 TV. 18,10,0, P. & P. 8/0 
3,000 W. 67.10.0, P. * r. 12/6 
7.500 W. 615.10.0, P. ft P. 20/- 




ADMIRALTY B.40 RECEIVERS 

Junl released by the Ministry. High quality 10 valve receiver 
manufactured by Murphy. Coverage in a bands OOOKc/s-SQMc/a. 
I/F 600Kc/s. Incorporates 2 R.F. and 3 J.F, stages, band- 
pass Alter, noise llmlter, crystal controlled B.F.O., calibrator 
I/F, output, etc. Built-in speaker, output for phones. Operation 
160/230V a.c. »lie 19i X 13J x 16in. Weight 1141b. OHerert 
in good working condition. 188.10.0. Carr. so--. With circuit 
diagrams. Also available B.41 I..F. version of above 15Kr/a.- 
700Kc/b. £17. 10.0. Carr. 30/-. 



S0LARTR0N CD7HS.2. DOUBLE 
BEAM 
OSCILLOSCOPE 

.'.: extremely bigh 
iiuality oscilloscope 
originally costing 
£400. Switched 

beam. Identical If], 
Y2 AmpUSera d.c. 
toBMo/s. Sensitivity 
3mV/CM to 

1 00 V /CM. Time 
base 10ji/sec. to 
10M /sees .Calibrator. 
X ainjilifier d.c. to 
2 5Me/s. Z Modulation. 1 10/220/260V, 
a.e, Supplied in gootl working order. 
£05, carriage £2, or available as received 
from Ministry nnservieed £50, carriage £2. 
(Handbooks 12 extra,) 




AVO CT.38 
ELECTRONIC MULTIMETERS 

High quality 97 range instrument which 
measures a.c, and d.c. Voltage. Current, 
Resistance and Power output. Ranges 
d.c. volts 2D0mV- 10,000V, (lOmegfl- 
llOmegn input). B.C. current 10/xA 
25 amps. Ohms: 0-l,OOOmsgQ . A.c. 
volt 100mV-2S0V. (with H.P. measuring 
bead up to 250Mc/s), A.c. current 
lO/uA.25 amps. Power output 50 micro- 
watts-5 watts. Operation 0/110/200/ 
260V. C. Supplied in perfect condition 
complete with circuit lead and R.F. 
probe 125, Carr. 15/-. 



MARCONI TEST EQUIPMENT 

KX-M1L1TARY RECONDITIONED. 

TF 144G STANDARD SIGNAL GENERATORS, 

8SKc/g.25Kc/8, 125, carr, 30/-. 

TF.885. VIDEO OSCILLATOR. 0-5Mc/s, £45, 

Carr. 30/-, 

T^.ISSM. BEAT FREQUENCY OSCILLATOR 

0.40kc/s, 200/250 V a.c. (20, carr. 30/-. 

All above oflered in excellent condition fully. 

tested and checked. 

TF. 1100 VALVE VOLTMETEB, Brand New. 

£60. TF, 1267 TRANSMISSION TEST SET, 

"Brand New, £75. 




AM/FM SIGNAL GENERATORS 

Oscillator Test 
No. 2. A high 
quality precision 
instrument made 
for the ministry 
by Alrmec. Fre- 
quency coverage 
20-SOHc/s AM / 
C.W. / FM. Incorporates precision dial, 
level meter, precision attenuator ljjV- 
I00MV. Operation ttom 12V d.c. or 
0/U0/200/250V a.c. Size 12 X 8! X Bin. 
Supplied in brand new- condition complete 
with all connectors fully tested, £46. 
Carr. 20/-. 




TYPE ISA DOUBLE BEAM 
OSCILLOSCOPES 

An excellent general 
purpose D/B oscilloscope. 
T. B . 2c/a-7 60Ke/s , Band- 
width 5-GHc/s. Sens!- 
tivity 33MV/CM. Opera- 
ting voltage 0/ 110/200/ 
250V a.c. Supplied In 
excellent working condi- 
tion, £22.10.0. 

Or complete with all 
accessories, probe, leads, 
lid, etc., £25. Carriage 




Variable f/oftaee TRANSFORMERS 



Br^nd new, guaranteed and carriage paid. 

High quality construction. Input 230V 60-60 cycles. 

Output full variable from G-200V. Bulk quantities available. 

1 amp.— £5.10.0; 2. 5amp.— £6.15.0; 5 amp. £9.15.0 ; 

B amp.— £14.10.0: 10 amj.. £18.10.0; 12 amp.- -£81; 20 amp.— £87 



i>'i 



PRINTED 
CIRCUITS 

Five assorted prin- 
ted circuit boards 
with transistors, 
diodes, resistors, 
condensers, etc. 
Guaranteed mini- 
mum 20 transistors. 
Ideal for experi- 
menters, 6 uoards 
for 10/-. P. & F. 2/-, 





TE22 SINE SQUARE WAVE 
AUDIO GENERATORS 

Sine; 20c/s to 
200kc/s on 4 
bauds. Square: 
20c/s U» 30kc/e. 
Output imped- 
ance 5,000 ohms, 
200/2S0V a.e, 

Supplied brand 
new and guaran- 
teed with instruc- 
tion manual and leads, £16. Carr. 7/0. 

DUBUJER HITBOGEL COHDEHggRS 
Brand new S mfd. 8<K)V 8/8, P, 4 P. 2f-; 
2 mfd. 6,000V 42/6, P. & P. 8/-. 

LUCAS 20/0/20 AMMETERS 
Brand new boxed. Suitable car/ motor- 
cycle. 12/9, P. A P. 2/-. 

LELAJD MODEL 27 BEAT FKEQTJEHCY 
OSCILLATORS. 0-20K0/I. 
Output CK or S0O ohms, 20O/25OV a.c. 
Offered in excellent condition £12.10,0. 
Carr. 10/- 

HAISBX BWB BUDGES 
52 ohm. 88/0, P. & P. 3/0. 




AV0METERS 

Supplied in ex- 
cellent condition, 
fully tested and 
checked. Com- 
plete with prods, 
leads and instruc- 
tions. 
Model 47 A 

£8.18.8. 
Model 7 £18.10.0. 
Model S £18,0.0. 
P.* P. 7/6 each. 



S0LARTR0N MONITOR 

OSCILLOSCOPE 

TYPE 101 

An extremely high quality oscilloscope 
with time base of 10(1 /sec. to 20m/scc. 
Internal Y amplifier. Separate mains 
power supply 200/250 V. Supplied in excel- 
lent condition with cables, probe, etc., as 
received from Ministry. £8.18.8. Carriage 
30/-. 

R.C.A. MR SPEAKERS 

8iu, 3 ahm speakers in metal case. Black 
crackle finish to match our 88 Receivers. 
Available Brand New and Roxcd with 
leads. fit/S. Carr. 7/0. 



G.W.SMITH 

& Co. (Radio) Ltd. 
3-34 Lisle St., W.C.2 

ALSO SEE OPPOSITE PAGE 



394 



MULTIMETERS for EVBRY purposel 



MODEL AS-100D. 
lOOKn/VOLT Din., 
mirror scale. Built- 
in meter protection. 
/ 3 / 12 / 60 / 120 / 
300 / 800 / 1,200V. 
d.c 0/6/30/120;300 
600V. b.c. 0/10jnA/ 
S/60/300MA/12 Amp. 
0/2K / 200K f 2M / 
200M(1. —20 to 
+ 17dB. £12.10.0. 

P * P. 316. 





MODEL TE-10A. -JiiOkO. 

Volt, 5/20/50/250/500/2,600 

V. d.c, 10 / 80 / 100 / 800 / 

1,000V. a.c. 

0/6G/M/2-5 U1A./3M in A. 

d.c, 0/8K/fi megohm. —20 

to + 22dB. 

10-0, 100 mid. Q-100-b'l 

mM. W6. P- * P. aw. 



MODEL TE-70. 30,0(m 
O.P.V. o.'s.'is/iio/ano.- 
600/ 1,200V. d.c. 0/8/ 
30 / 120 / 600 / 1,200V. 
a.c. 0/30fiA / 3/30 
300m A. 0/16K/160K, 
1-6M ,' lSmegohm, 
£5,10.0. P. i- P. 3/-. 





—20 

40/6. 

LAFAYETTE 

57 Range Super 
50,000 O.P.V. 
Multimeter. D.c. 
Volts 12BV-1000V, 
A.c. Volte 1 ,BV- 
1O00V. D.c. Current 
■J5|j.\-I« Amp. 
Ohms. 0-15 Meg [J. 
dB. — 20 to + SldB. 
Overload Protec- 
tion. £12.10.0. 
Co^I■. 3/6. 



MODEL 2501. ~2~,000 
O.P.V. 0.' 10/60/500/ 

2,500 V. .l.o. 0,' 10/80/ 
500/2.0OOV. a.c. 

0/2megohin. 0(280 in A. 



to 



I*, ft P. a/n. 



+ 36(IB. 




MODEL ZQM TKASSISTOR CHECKER 

It baa the tallest capacity for 

checking on A, E and Ico. 

Equally adaptable for 

checking diodes, etc. Spec: 

A: 0- 7-0 9967. B: 0-200. 

Ico: 0-60 mlcroamps 

0-BmA. Resistance lor 

diode 200Q-1MD. 

Supplied complete with 

instructions, battery and 

lead*. 16.19.6. P.ftP.2/6. 





H0SIDEN DH04S 
2-WAY STEREO 

HEADSETS 
Each headphone con- 
tains a Si In woofer 
and a | in tweeter. 
Built in individual 
level controls. 

2o-ia,00Qc/s. 8fl imp. 
with cable and stereo 
plug. tS.19.6. F.iP. 
2/6, 




F.M. WIRELESS 
MICROPHONES 

94-104Mc/s. Transistor- 
ised. Operates from 9V 
battery. Complete with 
additional secret tie-clip 
m Icrophone . L 1st ii 1 2 . 10 . 
ONLY 18.15.0, P. * P. 
2/6. 

These cannot be operated 
in U.K. 



TRANSISTORISED 

TWO-WAY 

TELEPHONE 

INTERCOM 

Operative over amazingly 
long distances. Separate call 
and press to talk buttons. 
2-wire connection. 1000' b of 
applications. Beautifully fin- 
ished in ebony. Supplied 
complete with batteries and 
wall brackets. 
18,19.6. P. * P. 3/6. 





SEW MODEL 500,30,000 
O.P.V. with overload 
protection. Mirror scale. 
/ 0-6 / 2-5 / 10 / 25 / 100 ( 
250 / 500 / 1,000V. d.c. 
/ 2-5 / 10 / S6 / 100 I 
250 / 500 / 1,000V. a.c. 
0/50jiA/5/50/500iiiA. 
12 ump. i I.e. 0/60 fK6. 
Mcg./OOmegohin £8.17.8. 
I'ost paid 



MODEL TE-12. 20,000 
O.P.V, 0/0-8/ 30; 120/600 
1,300 / 3,000 / 6.0O0V. d.c. 
1/6/30/ 120/600/ 1,300V. a.c. 
/ OOfiA / 6 / 60 / QOOMA. 
/ 6K / 600K / dmeg./eo. 
Megohm 50FF. 2 MFD. 
£5.10*. P.* P. 3/6. 

MODEL TE SO 





£4,17.6 
TE-51. MEW 20.000 n 
VOLT MULTIMETER. 

O/<3,fu0.'120, 1.200V. a.c. 
/ 3 / 30 / 60 / 300 / 600 i 
3,000 V. d.c. 0/eOuA/ 
12/300 m A. d.c. i> (Silk" 
Bmeeohin. 85 -. I' t I'. 



30.000 
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available: H.F. 35'- 
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watt ampliOer. 89/8. 

PZ4 Power Supply Unit 99/8. 

Stereo 25 Preamp., £9,19.6. 

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396 






VOL 4 No. 6 
June 1968 



PRACTICAL 

ELECTRONICS 



THE AIR FORGE AND ELECTRONICS 

The fiftieth anniversary of the Royal Air Force is a 
fitting occasion to recall the close relationship that has 
always existed between this Service and the branch of 
technology we now know as electronics. Their histories 
are closely interwoven. The needs of air defence were 
chiefly responsible for the sudden growth of electronics. 

When the R.A.F. was formed in 1918 wireless com- 
munication was already established, but still rather a 
novelty. Fortunately, government advisers on defence 
matters anticipated important future developments in the 
use of electro-magnetic waves, and a Radio Research 
Board was set up in that very same year. Thus was 
brought into being the nucleus of the official machinery 
which later facilitated consultations with persons such as 
R. Watson-Watt, destined to become the father of radar. 

Once the feasibility of locating aircraft by radio had 
been demonstrated, many of the finest brains from 
universities, the radio industry, and government scientific 
departments were harnessed to the task of converting this 
idea to a practical reality. As is now well known, the first 
chain of R.D.F. stations was installed around the coasts of 
Britain well before the outbreak of war in 1939. 

Furthermore, as we now realise, the door leading to a 
future "electronics" era was dramatically pushed open by 
these heroic backroom efforts of scientists, physicists, and 
engineers in the late 30's. 

In amateur circles there is to be found an especial regard 
for the Royal Air Force. No other service depends so 
heavily upon signals and other branches of electronics. In 
1939 hundreds of radio amateurs entered the R.A.F., some 
to perform signal duties, others to be assigned to special 
training on the secret R.D.F. equipment. Subsequently, 
thousands of other men and women from all walks of life 
became initiated into the strange world of radio — or the 
even stranger one of radar — during those war years. 

Many of these ex w/op's and radar mechanics have 
retained their interest and have applied this fortuitously 
acquired knowledge to good effect in Civvy Street. The 
current general awareness of electronics, and the adoption 
of this subject as a useful and intellectually stimulating 
recreation by a great many lay persons, are in large 
measure due to the training and experience provided by the 
armed forces, and the R.A.F. in particular. 

Today the future pattern of the Royal Air Force is the 
subject of much speculation. The move from manned 
aircraft to remotely controlled missiles can only mean a 
greater preponderance of electronic devices and systems. 
Whatever changes take place, the role of electronics is 
bound to be pre-eminent. 

F. E. Bennett— Editor 



THIS MONTH 



CONSTRUCTIONAL PROJECTS 



RADIO CONTROL SYSTEM 

FOR MODEL BOATS 398 

CAMERA TRIGGER 414 

P.E. ANALOGUE COMPUTER 429 

DRUMMER'S WHOOSH 443 



SPECIAL SERIES 



NUCLEONICS FOR THE 
EXPERIMENTER— 8 417 

TRANSISTOR AMPLIFIER 
DESIGN— 5 422 



GENERAL FEATURES 



EPOXY RESINS 410 

INGENUITY UNLIMITED 420 



NEWS AND COMMENT 



EDITORIAL 397 

POINTS ARISING 409 

SPACE WATCH 413 

ELECTRO NO RAMA 428 

MARKET PLACE 447 

READOUT 448 



Our July issue will be published on 
Friday, June 14 



AH correspondence intended tor the Editor should be addressed to: The Editor, PRACTICAL ELECTRONICS, George Newnes Ltd., Tower 
House, Southampton Street, London, W.C.2. Advertisement Offices: PRACTICAL ELECTRONICS, George Newnes Ltd., 15/17 Long Acre, 
London, W.C.2. Phone; 01-836 4363. Telegrams: Newnes London. Subscription Rates including postage for one year, to any part of 
the world, 36s. © George Newnes Ltd., ] 968. Copyright in all drawings, photographs and articles published in PRACTICAL ELECTRONICS 
is specially reserved throughout the countries signatory to the Berne Convention and the U.S.A. Reproductions or imitations of any of 
these are therefore expressly forbidden. 



MULTI CHANNEL 



RADIO 



CONTROL 

M 




FOR MOOeL 6° A • 




The relatively simple transistorised multi-channel 
control system described here was designed 
specifically for controlling a 34in model diesel powered 
Vosper R.A.F. Crash Tender, Circuit and con- 
structional details are given for the radio transmitter, 
receiver and control arrangements, including those for 
rudder and throttle actuator mechanisms. No special 
tools are required other than perhaps a power hand 
drill, although a multi-range meter is desirable and an 
oscilloscope is an advantage. The overall model with 
electronics will appeal to the do-it-yourself modeller 
who has a certain amount of electronics knowledge. 

SINGLE OR MULTI-CHANNEL? 

Undoubtedly the simplest control arrangement is 
"single-channel" operation in which only one item of 
information is transmitted at any one time. This can 
be quite effective, although special operating tech- 
niques may have to be evolved, particularly when high 
speed models are used, so that function selection is not 
unduly delayed. 

In the case of model aircraft, the flying technique 
for single channel working differs completely from 
normal multi-channel practice. Therefore, it would 
seem to be a very natural progression to the more 
versatile "multi" techniques, which enable simultaneous 
movements of various controls to be made, particularly 
if the cost of such a system could be kept low. 

AIRCRAFT OR BOAT? 

The scope of "multi" aircraft control can be very 
rewarding, but the following points were the decisive 
factors in selecting a boat for using the control system 
described. 

Cost of the installation 

A boat or land vehicle control system need not be as 
complex as its aircraft counterpart, a four-channel 
system being usually quite adequate for controlling 
a boat, even at high speed. Surface vehicles are not 
seriously affected by equipment weight, size, or power 
consumption restrictions generally imposed by an 
aircraft of practical proportions. 

This gives the home constructor much more scope 
to use materials and components which are readily 
available, rather than to have to purchase the relatively 
expensive, compact, and lightweight items generally 
required for aircraft control. There is no particular 



need to miniaturise the circuitry or actuators; with a 
boat. of 34in overall length, lack of space is not a 
problem to be encountered here. 

Loss or damage 

In the experimental stages, particularly with home- 
built equipment in the hands of newcomers to model 
control, there is a very real risk of damage, or even a 
complete write-off, in the case of a powered aircraft, as 
a direct result of some form of loss of control. 

Adequate operating facilities 

Unless one joins a club it is difficult to find suitable 
large open spaces for aircraft flying without undue 
aerial hazards. It must be remembered that a powered 
aircraft in free flight at speed is potentially a dangerous 
projectile and serious personal injury has been known 
to occur to spectators. There are still plenty of 
smooth stretches of water to be found of quite sufficient 
size for putting a boat through its paces without risk 
of annoyance to anyone. Most marine diesels are 
equipped with silencers to reduce noise. 

The effective working range of the transmitter/ 
receiver combination described in this article is about 
a quarter of a mile. In practice, this was found to be 
more than adequate, because even at 200 yards distance 
it becomes difficult for the operator to ascertain the 
boat's position and attitude in the water. 

BASIC ARRANGEMENT 

The basic scope for control of a boat is probably less 
than that for an aircraft, and in order to justify the 
selection of a "multi" system, a high-speed planing hull 
was selected, capable of good manoeuvrability at speed. 
Because of the low power/ weight ratio achieved with 
electric propulsion, an ample size of diesel engine was 
chosen as the power unit. This was installed in an 
''Aerokits" R.A.F. Crash Tender available in kit form 
in plywood. The 34in model is used. 

This boat is ideal for an installation of this type, the 
hull being conveniently divided, by bulkheads, into 
five compartments {see maker's plans). It is very wise 
if an internal combustion engine is used, to keep one 
compartment amidships reserved for the engine, fuel 
tank, and perhaps throttle gear, as these miniature 
engines tend to become dirty, exuding a mixture of soot 
and uoburnt fuel — the penalty for throttling a diesel 
engine. 




p ^ToNE B * 



The bow compartment (No. 1) (see maker's plans) is 
sealed off and filled with buoyancy material; No. 2 
compartment (wheelhouse) is used as the main elec- 
tronics area, as this is readily accessible but is well 
protected and well clear of any spray that might occur 
at speed. This compartment accommodates the radio 
receiver, preamplifier, and both control motion panels. 

The receiving aerial plugs into a socket fixed to the 
deck adjacent to No. 2 compartment. No. 3 compart- 
ment is the engine room with throttle control and fuel 
tank. No. 4 houses the battery, relays, and the iso- 
lator switches. No. 5 compartment is occupied fully 
by the steering actuator and the actuator supply 
battery. It is probably a good idea to mark these 
compartments on the.plans. 

If polyurethane foam is inserted ahead of bulkhead 
BI, holes of about J in square should be made in the 
bulkhead. 

The second compartment houses the four perforated 
s.r.b.p. modules: the receiver (aft), the pre-amplifier 
(port side), rudder control (starboard side), and throttle 
control (forward). These four modules are easily 
recognised in the circuit diagram, each being indicated 
by a hatched line box (see Fig. 2). The complete 
circuitry in the boat is shown; the transmitter will be 
described later. 



E .J. PEPPER c 




En 




Fig. f. Block 
diagram illus- 
trating the basic 
operating prin- 
ciples of the 
radio control 
system 



'*• *».#. 



£ 



TWO BASIC SYSTEMS 

There are two basic systems of control in general use, 
and there are also two main ways by which the control 
intelligence can be made to actuate the controlled 
member (see Fig. !). 

Progressive control 

Progressive control is usually simplest, but less 
precise, being in principle an "open loop"' arrangement 
of integration where the controlled member will move 
at more or less constant rate in the desired direction 
until it is checked. 

Proportional control 

This is a true "closed loop" servo position control. 

The simplicity of the system to be described stems 
from the fact that it permits simultaneous transmission 
of one progressive system and one proportional system, 
the former being used to actuate the throttle, i.e. 
commands "close", "open", and "hold", the latter to 
steer the boat. 

The rudder assumes the angular position corres- 
ponding to that set up on the steering "wheel" on the 
transmitter unit, regardless of the load conditions on 
the rudder. To achieve this it is necessary to feed 
back the rudder position to the controller by means of a 
potentiometer (VR2) ganged to the rudder shaft. 

CONTROL PRINCIPLE 

The two controls, rudder and throttle, may be oper- 
ated individually or simultaneously, and the principle 
of operation may be readily understood from Fig. 3. 
The transmitted 27MHz carrier is 100 per cent modu- 
lated by a square wave of adjustable mark /space ratio 
to correspond to rudder control, and at three pre- 
selected fundamental frequencies to provide throttle 
control. 

The appropriate frequency (110Hz, 600Hz, 400Hz), 
corresponding to "increase", "decrease", and "hold" 
throttle respectively, can be selected by a centre biased 
three-position key on the transmitter, without affecting 
the pre-set mark /space ratio. The mark /space ratio 
of the square wave is variable from 1 : 10 to 10 : I, for 



a 



RUDOER SERVO 



THROTTLE SERVO 



4- I 




c 
o 



I 



s 

! 



A, 

E 

o 
U 



400 




f.4O0 Hi 



f- 600 Hz 



f=«0Hl 



Average D.C. level (low) 



Average D.C [evel (high) 






Average QC. level (intermediate) 







Monostable set by 
negative edges only 



Average D.C. (level) 




tn 



M0N0STAW.E 



(a) Steering control waveforms Port ftudder (b)Steering control waveforms Starboard (c) Steering control waveforms Rudder (^Corresponding Throttle control waveform* 

Rudder Amidships 



;40QHi 'HOLD' throttle/Intermediate D,c\ f.600Hz 'CLOSE 'throttle (High 0£; level) f-MOHz 'OPEN" throttle (Low D.G. level) 
\ level I 



NOTES- 



(l)The DC. level of the Rudder waveforms does not change with frequency (2) The Throttle waveform is not affected by change of Rudder Mark /Space ratio 

Fig. 3. Steering and throttle control waveforms 



any selected frequency and is set by the steering wheel 
control on the transmitter, a ratio of I : 1 corres- 
ponding to "rudder straight". 

After detection by the receiver, the square wave 
signals are converted to d.c. levels which in turn 
actuate relays. These control the d.c. motors which 
rotate, in the appropriate direction, the actuator lead 
screws. 

The general description of the system will now be 
followed by a more detailed account of the various 
functional units. However, it is emphasised at this 
stage that general information on constructing the boat 
is excluded since it is outside the scope of this magazine. 
It is expected that the constructor will acquire the boat 
kit with instructions through a retailer. 

A kit of accessories for this model is available 
through retailers from Keil Kraft. The electronics 
are not generally available in complete kit form; con- 
structors will find that all electronic parts are obtainable 
through the usual retailers. 

RADIO RECEIVER 

It is an undisputed fact that, because of their selec- 
tivity performance, superheterodyne receivers are to be 
preferred to t.r.f. types; nevertheless super-regenerative 
receivers can give excellent results and are undeniably 
simple. If the constructor has no intention of becom- 
ing involved in active competition work, where a super- 
net could offer advantages, he would probably do 
well to compromise and go for a super- regenerative 
receiver, which is simple and inexpensive while offering 
adequate performance. 

At the high transmission frequency used, it would 
have been very difficult to have achieved adequate r.f. 
amplification with a conventional tuned radio fre- 
quency (t.r.f.) receiver, whereas the super-regenerative 
receiver is capable of providing tremendous amplifi- 
cation, provided that faithful reproduction of the 
modulation signal is not an important criterion. 



As we are dealing with "clipped"' rectangular wave- 
forms the effects of signal distortion are of little 
consequence. 

The principle of the super-regenerative receiver is to 
employ large amounts of positive feedback, to increase 
the overall gain or sensitivity. This "regeneration". 
or "reaction" as it was once known, is arranged to 
render the circuit alternatively oscillatory and non- 
oscillatory at a fairly rapid rate. 

In ordinary t.r.f. receivers, the amount of regenera- 
tion possible is limited by the tendency towards 
instability, leading to continuous oscillation or "howl". 
The super-regenerative receiver makes full use of this 
phenomenon, and sufficient positive feedback is applied 
to ensure that self-oscillation will definitely occur. 

TR2 is the super-regenerative detector stage and 
regeneration is applied via C7 from collector to emitter 
from the tuning coil L3. 

As self-oscillation is assured, the strong resulting a.c. 
level is rectified by the base/emitter junction of TR2 
to provide a d.c. bias signal. This bias builds up 
progressively on C4 and C6 such that the gain of TR2 
progressively reduces until the transistor cuts off, and 
oscillation ceases. 

The charges on C4 and C6 immediately begin to 
leak away after cut-off occurs, and ultimately TR2 will 
again commence to conduct, the current and gain 
increasing until oscillation again ensues, when the 




401 




jfl^SE^^^^ 



process repeats itself. The 
time constants C4-R5 and 
C6-R7 are selected such 
that the periodic bursts of 
oscillation (referred to as 
"squegging*') occur at some 
low radio frequency, which 
is not particularly critical, 
and will be found to in- 
crease with the antenna 



signal strength, normally being between about 
30-l00kHz. This is well out of the signal modu- 
lation frequency range, and can be filtered out after 
detection. 

It can be seen, therefore, that there is a substantial 
portion of time in each period of "squegging" when the 
gain of the receiver is exceptionally high, but when self- 
oscillation does not exist. . The gain during this period 
is far higher than could be achieved, with stability, in 
any single stage "conventional" t.r.f. receiver. 



RECEIVER CONSTRUCTION At DETAILS 



COMPONENTS . . . 



Resistors 






R! 39kQ R4 IkQ 


R6 


22k a 


R2 JSkn R5 2-2kQ 


R7 


ika 


R3 IkH 






All 10%, £ watt carbon 







1 5pF ceramic 
0-002/xF mica 
25pF ceramic 
2 F F elect. 25V 



Capacitors 

CI 22pF ceramic *C5 

C2 220pF mica C6 

C3 0-00 1/iF mica *C7 

C4 000 1 /iF mica C8 

C26 002/xF polyester (additional squegging filter) 
*C5 and C7 may be altered in value so that the dust core 
in L2/3 is about mid travel for optimum tuning 

Transistors 

TRI.TR2 OCI70orOC17l (2 off) 

Coils 

LI 12 turns 28 s.w.g. enam. wire close wound on 
Meosid yin polystyrene former with adjustable 
core. Tapping is taken 2 turns from the "earthy" 

end of the winding. 

OUTPUT TO C9 ON 
PREAMPLIFIER BOARD 





4X4 

COPPER CLAD s.r.b.p. 



NOTE: BASE AND 
SCREEN WIRES TO 
SAME PIN ON 
TR1 AND ON TRZ 



AERIAL INPUT 



L2/3 fin Aladdin former with dust core. L3 wound 
first— 9£ turns 28 s.w.g. enam. wire close wound. 
L2 2 turns 28 s.w.g. enam. wire wound on top of 
L3 at "TRI collector" end 

L4 R.F. choke, 38 s.w.g. enam. wire in single layer on 
£in Neosid former with dust core 

Miscellaneous 

Aerial, 14 in whip type made from 20 s.w.g. brass or 
nickel silver wire with wander or banana plug fitted 
to one end. Socket for aerial. Plain or perforated 
copper clad s.r.b.p. sheet (see Text) 4in x 4in. Pins for 
perforated board 




Fig. 4, Component layout and wiring of the receiver panel 



402 









Because of the fact that TR2 operates very close to 
its cut-off point, its characteristic is non-linear, and it is 
this non-linearity which provides the essential charac- 
teristic for detection of the modulation of the carrier. 
Therefore, TR2 performs the dual role of high gain 
r.f, amplifier and detector. 

If no signal is being received, then self-oscillation is 
induced at a higher level of collector current, or gain, 
and hence any circuit noise is greatly amplified in the 
absence of a carrier. It is because of this inherent 



characteristic that the super-regenerative receiver is 
affectionately referred to by some as a kt rush-box". 

The selectivity of a super-regenerative receiver is 
inherently poor, and hence is prone to receive simul- 
taneous transmissions, on neighbouring frequencies, 
from other model control operators in the vicinity. 
This undesirable feature is to some extent offset by the 
tendency of the circuit to "latch on" to the strongest 
signal present, and suppress any weaker signals 
received. 






PREAMPLIFIER CONSTRUCTIONAL DETAILS 




. t)1 Ctl 

% a ^ c # ® ^ @* ®* ®f 




COPPER SURFACE 
ISOLATED FROM ALL 
PINS EXCEPT THOSE 
HARKED E 



<•) <•) ® <g> % 




TO L3 

ON RECEIVER 



TO R20 ON STEERING BOARD 
AND C22 ON "THROTTLE" BOARD 

T0-BY1 TO R8 ON RECEIVER BOARD 

Fig. 5. Component layout and wiring of the preamplifier panel 



COMPONENTS . . . 



Resistors 

R8 470Q 
R9 lOOkQ 

RIO 56k<> 
Rll lOkll 



RI2 lOkn 

RI3 47kQ 

RI4 39k Q 

RI5 8-2k£2 



RI6 lOkQ 

RI7 lOOka 

RI8 27kQ 

RI9 2-7 k.Q 



All 10%, £ watt carbon 

Potentiometer 
VRI 250kfi carbon min. preset 



CI 3 50/iF elect. 6V 
CI4 JSfiF elect. 12V 
CIS 001/iF paper 



Capacitors 

C9 IO M Felect. 12V 
CIO 25 M F elect. 12V 
CM 25**F elect. 12V 
CI2 0047^F paper 

Transistors and Diodes 

TR3, 4, 5 2N3702 or 2N3703 (3 off) 
D1.2 IS44 or ISI30 or OA200 

Miscellaneous 

Plain or perforated s.r.b.p. sheet (see text) 4in 
Pins for perforated board 



3in 




103 



The "squegging" action of 
the receiver can cause un- 
wanted r.f. radiation from a 
receiving antenna connected 
directly to the input. Indeed, 
the initial experiments, per- 
formed tn an attic workshop, 
caused considerable interfer- 
ence to television receivers via 



aerials in the immediate vicinity. This was eliminated 
and a 6dB gain achieved by fitting an r.f. stage TR1. 

This acts as a buffer between the "squegging" 
detector TR2 and the antenna, and is merely a class A 
amplifier biased by RI and R2 in the base, and R3 and 
C3 in the emitter circuit, for stable operation. The 
output at the collector is loosely coupled by L2 to L3. 

The effect of the antenna loading is reduced on the 
detector stage, thereby increasing its performance, 



STEERING CONTROL CONSTRUCTIONAL DETAILS 



RUDDER FEEDBACK 
A /TO SLIDER VR2 




TRIO 



TR11 



COPPER SURFACE 
ISOLATED FROM ALL 
PINS EXCEPT THOSE 
MARKED E 




TO TR5 COLLECTOR 
ON PRE-AMPLIFIER 



^ 

TO RLB COIL 'PORT 

TO RLA COIL c- *- 

'STARBOARD' F '&* 6 ' Component 



COMPONENTS . . . 



layout and wiring of the steering control (rudder) panel 

1 



Resistors 










R20 lOkil 


R24 


47kQ 


R28 


1 SOkfl 


R2I 4-7kli 


R25 


22kO 


R29 


8-2kn 


R22 27k£2 


R26 


27kQ 


*R30 


ISkQ. 


*R23 IOki> 


R27 


IkQ 


*R31 


nkn 


All 10%, i watt car 


bon 









* R23, R30, and R3I may require adjustment on test 

Potentiometers 

VR2 5k!2 linear carbon or wirewound min. 
VR3 I M12 carbon min. preset 

Capacitors 

CI 6 2<VF elect. 16V CI 9 

CI7 I^f tantalum or paper C20 

12V 
CIS OI^F paper 

Transistors and Diodes 

TR6, 7, 8, 10 2N3702 or 2N3703 (4 off) 

TR9, 1 1 2N3707 {2 off) 

D3, 4 Z8-2 (Brush) or OAZ246 (Mullard) 

Zener diodes (2 off) 
D5 Z56 or OAZ242 Zener diode 

D6, 7 [S44, ISI30, or OA200 (2 off) 




0-l^iF paper 
8/LiF elect. 25V 



C2I \/iF paper 



Relays 

RLA, RLB 12V 700£1 type MH2 with two changeover 

sets of 1A contacts (Keyswitch) 
or type 4I90GD (S.T.C.) (2 off) 
(Normal open pair of contacts used) 

Switches 

S2 Single pole toggle 

S3T 

g^ ("Part of Drive System, see Part 2 

Miscellaneous 

M02 Motor 3V 6,000-7,000 rev/min (Ripmax Orbit 

type 505) 
Plain or perforated s.r.b.p. sheet 4in >: 4in. Pins for 

perforated board 



404 



whilst the antenna loading circuit itself is flatly tuned 
by Ll-Cl prior to amplification by TR1. 

The high frequency "squegging" component at 
TR2 output is filtered out by C26. 

PRE-AMPLIFIER 

Satisfactory operation of the controls depends 
entirely on the preservation of a good rectangular 
waveform after detection by the receiver. This is 
effected by the use of a high gain pre-amplifier (which is 
normally saturated), together with a degree of noise 
rejection filtering. Due to the saturated condition of 
the amplifier, it is quite stable, and the limiting action 
is effective in removing the inherent noise generated by 
the super- regenerative circuit. 

The pre-amplifier comprises TR3-TR5 in a circuit 
which is optimised to clip and square the full range 
mark/space ratio for minimum signal strength con- 
ditions, and provides automatic d.c. restoration of the 
rectangular wave relative to the zero level for all 
signals. 

Potentiometer VR1 is an optional preset control, 
which is fitted to the prototype, and can be adjusted to 
give optimum noise rejection at the limit of the working 
range of the transmitter. Some degree of noise 
rejection is provided by CI 2 and CIS. 

PROPORTIONAL RUDDER CONTROL 

The resultant "clean" rectangular waveform appear- 
ing at TR5 collector contains an average d.c. component 
proportional to the mark/space ratio, but independent 
of the frequency. This component is extracted by 
the smoothing circuit R20 and C16 and buffered by 
emitter follower TR6, prior to being used as a "refer- 
ence" voltage. This voltage is to be compared with a 
feedback reset voltage proportional to the actual 
rudder position as derived by VR2, which is driven 
mechanically by the rudder shaft, and is some fraction 
of the battery voltage. 

The comparison is made at the input of the d.c. 
operational amplifier TR7, TR8, TR9, whose closed 
loop gain is controlled by VR3, the feedback potentio- 
meter, to something around 15. 

The quiescent state of the servo is that associated 
with an amplifier output of about half the battery 
voltage, when the input currents derived from the 

BUOYANCY 
COMPARTMENT 1 



ELECTRONICS 

COMPARTMENT 2 



BATTERY 
AND RELAYS 




IMPORTANT 

Readers intending to construct this radio con- 
trolled model boat are advised that, before 
operating in the U.K., the appropriate "model 
control" licence must be obtained. This licence, 
which is allocated for model control only at 
26 96 to 27 28MHz for a radiated power not 
exceeding I -5 watts, can be obtained, upon pay- 
ment of £1 (sterling), from the Radio Services 
Branch, G.P.O. Headquarters, St. Martins-le- 
Grand, London, E.C.I. 

reference source and the feedback potentiometer are 
approximately equal. If, however, the reset voltage 
differs from that required to obtain this state by about 
0-25 volt or so, the amplifier will drive hard to satura- 
tion or cut off depending on the polarity of the difference 
voltage. 

A deadband circuit embodying Zener diodes D4 and 
D5 follows the amplifier, which inhibits operation of 
succeeding circuits until the "error" voltage exceeds 
about half that necessary to saturate the amplifier in 
either direction. This "error" voltage corresponds 
to about 5 degrees of arc of the steering control at the 
transmitter (270 degrees helm to helm) and is experi- 
enced as lost motion. The deadband, however, creates 
a definite quiescent state for the control, in which the 
rudder relays and actuator motor are not energised, 
and hence once the rudder "homes" to the selected 
position, current consumption falls to a very low level. 

If a signal of more than 5 degrees helm is given then 
TRIOorTRl I. as appropriate, conducts and the asso- 
ciated port or starboard relay is energised which in turn 
actuates the helm motor. When the rudder nears the 
selected equilibrium position, the amplifier "zeros" 
and the relay is released. 

Limit switches are fitted at the extremes of lead 
screw travel which open the motor circuit for the 
direction selected, should hard helm be given. 

The servo system is simply and effectively stabilised to 
one overshoot by the phase lead circuit in the feedback 
path(R28, C17). 

Adjustment of the gain control VR3 will optimise the 
response, corresponding to minimum dead zone 
without any tendency to oscillate. 

As the distance from the transmitter increases, some 
waveform degeneration is experienced which results in 
a slight "wander" of the rudder position. Similarly 
as the batteries run down, the relationship between 



AERIAL TO 
BE FITTED 
TO DECK 



THROTTLE 
ACTUATOR, 

ENGINE AND 
FUEL TANK 



2VCELLAND 
STEERING GEAR 




helm position and rudder posi- 
tion will be observed to change 
slightly. In practice these effects 
were not found to be severe 
enough to be embarrassing. 

If desired, the effect of 
battery voltage deterioration 
affecting the rudder control 



can be easily compensated for by merely rotating the 
rudder potentiometer body, with respect to its fixing 
bracket, slightly, say every half hour or so during 
operation. 

PROGRESSIVE THROTTLE CONTROL 

The output of TR5 is differentiated by C22 and R32 
and fed to the throttle control circuit TR12-TR17. 



THROTTLE CONTROL CONSTRUCTIONAL DETAILS* 



COMPONENTS . . . 



Resistors 

R32 I5kf2 
R33 47kH 
R34 470kf2 



R35 3-9k£2 R39 27kQ 
R36 l80kH R40 3-3kD 
R37 4-7kH R4I 4-7kil 
All 10%, ± watt carbon 



R42 8 2kO 



C24 40^F elect. 16V 
C25 0-lfi.f paper 



Potentiometer 

VR4 lOOkft carbon min. preset 

Capacitors 

C22 0003/i.F paper 
C23 002/iF paper 

Switches 

S5 Single pole toggle 

S61 

cj >Part of Drive System, see Part 2 

Transistors and Diodes 
TRI2, 13, 14, 15, 17 2N3707 (5 off) 
TRI6 2N3702 or 2N3703 
D8, 9, 1 2, 1 3 I S44 or OA200 (4 off) 
D10 Z8-2 or OAZ246 Zener 
Dll Z5-6 or OAZ242 Zener 

Relays 

RLC, RLD 1 2V700QtypeMH2 with two changeover sets 
of IA contacts (Keyswitch)or type4!9GD (S.T.C.) (2 off) 
Normal open pair of contacts used 




Miscellaneous 

MO I Motor, miniature for throttle control with a 

short shaft (Keil Kraft) 
Plain or perforated s.r.b.p. sheet 4in x 4in 
Pins for perforated board 

OTHER ITEMS FOR ELECTRONICS 
Switch 

SI Single pole toggle 

Batteries 

BY I 15V made up from 12 nickel cadmium cells con- 
nected in series (Deac I 25V, 225mAh) 

BY2 2V l-6Ah lead acid cell 

Components for mechanical actuators given next month 




COPPER SURFACE ISOLATED 
FROM ALL PINS EXCEPT 
THOSE MARKED E 




(j) f <3> tins) ® 



TO TR5 COLLECTOR 
ON PRE-AMP 



RLC COIL 



Fig. 7. Component layout and wiring of the throttle control panel 



406 



Build Your Own Heathkit Electronics 

A kit for every interest — Home Workshop — Hi-Fi — Radio — Test — Amateur 



Latest STEREO TAPE RECORDER, STR-1 

Fully portable — own speakers 
Kit £58. 0. inc!. P.T, P.P. 10/6 
Ready-to-use £70. 6. incl. P.T. 
P.P. 10/6 

FOR THIS SPECIFICATION 
±- track stereo or mono record and 
playback at 7^,3i and Hips. Sound- 
on-sound and sound-with-sound 
capabilities. Stereo record, stereo 
playback, mono record and playback 
on either channel. IS transistor circuit for cool, instant and depend- 
able operation. Moving coll record level indicator. Digital counter 
with thumb-wheel zero reset. Stereo microphone and auxiliary inputs 
and controls, speaker/headphone and external amplifier outputs . . . 
front panel mounted for easy access. Push-button controls for 
operational modes. Built-in stereo power amplifier giving 4VV rms per 
channel. Two high efficiency 8* X 5" speakers. Operates on 230V 
a.c. supply. 
Versatile recording facilities. So easy to build — so easy to use. 





Latest STEREO AMPLIFIER, TSA-12 

12 x 12 watts output 

Kit £36. 10. less cabinet P.P.10/6 

Ready-to-use £36 {incl. cab.) P.P 10/6 

Cabinet £2. 5. extra 

FOR THIS SPECIFICATION 

17 transistors, 6 diode circuit. -1dB, .16 to 50,000Hz at 12W 
per channel into 8 ohms. Output suitable for 8 or 15 ohm 
loudspeakers. 3 stereo inputs for Gram, Radio and Aux. 
Modern low silhouette styling. Attractive aluminium, golden 
anodised front panel. Handsome assembled and finished 
walnut veneered cabinet available. Matches Heathkit models 
TFM-1 and AFM-2 transistor tuners. 

Full range power . . . over extremely wide frequency range. 
Special transformerless output circuitry. Adequately heat- 
sinked power transistors for cool operation — long life, 6 position 
source switch. 



High-performance CAR RADIO, CR-1 




Superb long and medium wave 
entertainment wherever you drive. 
Complete your motoring pleasure 
with this compact outstanding unit. 



8 Latest semiconductors (6 transistors, 2 diodes). For 12V positive or 12V 
negative earth systems. Powerful output (4W). Preassembted and aligned 
tuning unit. Push-button tone and wave change controls. Positive manual 
tuning. Easy circuit board assembly. Instant operation, no warm-up time. 
Tastefully styled to harmonise with any car colour scheme, High quality 
output stage will operate two loudspeakers It desired. Can be built for a 
total price. 

KIT (less speaker) £12.18.6 incl. P.T. Ready-to-use £19.12.6 

P. P. 4/6 6* x 4* Loudspeaker £1.4.5 extra. (less speaker) P.P. 4/6 



Latest Portable Stereo Record Player, SRP- 

Automatic playing of 16, 33, 45 
and 78 rpm records. All transis- 
tor — cool instant operation. Dual 
LP/78 stylus. Plays mono or 
stereo records. Suitcase port- 
ability. Detachable speaker en- 
closure for best stereo effect. 
Two 8in " 5in special loud- 
speakers. For 220-250 V a.c. 
mains operation. Overall cabi- 
net size 15 ft X 3} -: ttiln. 
Compact, economical stereo and mono record playing for the whole 
Family — plays anything from the Beatles to Bartok. All solid-state 
circuitry gives room filling volume. 

KIT £28,6.0 incl. P.T. P.P. 10/6 Ready-to-use £35.4.0 

P.P. 10/6 





SSU-1 




A wide range of 
SPEAKER SYSTEMS 

HI-FI SPEAKER SYSTEM. Model 
SSU-1. Ducted-port bass reflex cabi- 
net "in the white". Two speakers. 
Vertical/horizontal models with legs, Kit 
£12. 14. 6 P.P. 12/- Without legs, Kit 
£12. 0. incl. P.T. P.P. 7/6 



The BERKELEY SLIM-LINE 

SPEAKER SYSTEM, fully finished 
walnut veneered cabinet for faster con- 
struction. Special 12* bass unit and 4* 

frequency unit. Range 30- 
Size 26' 

attractive 



mid/high 
17,000Hz. 
Modern 
value. 
Kit £19. 10. 6. 



17* only 7i" deep, 
styling. Excellent 



P,P, 13/6 



Berkeley 



Ready-to-use £24. 0. 0. P.P. 13/6 



Transistor Portables 

UXR-1, now available in Modern 
coloured cases or leather. 

6 transistor, 1 diode circuit. 7 x 4in. 
speaker. LW and MW coverage. 
Case: brown leather, or colours 
navy blue, coral pink, lime green. 
Please state 2nd choice. 

Kit £12. 8. 0. Incl. P.T. Colour 
Kit £13. 8. 0. incl. P.T. Leather 
P.P. 4/6 

UXR-2, choice of black or brown 
real leather cases. 

7 transistor, 3 diode circuit. Battery 
saving circuitry. LW and MW 
coverage. Pushbutton wave change. 
Slide rule tuning. 

Kit £15. 10. 0. incl. P.T. Leather 
P.P. 6/- 



UXR-1 



SEE HEATHKIT MODELS AT: 
GLOUCESTER 

Factory and Showroom, Bristol Road. 

LONDON 

233 Tottenham Court Road, W.1. 

BIRMINGHAM 

17-18 St. Martin's House, Bull Ring. 

Demonstrations by arrangement. 

Deferred terms available over £10 (U.K. only). 

Prices quoted are Mail Order prices. 



Send 
for 

Latest 
FREE 

Catalogue 

36 pages, 
many 
models 
in Colour 




UXR-2 

HEAT 



Please address all enquiries to 

DAYSTROM LTD., Dept. P.E.5, GLOUCESTER 

Please send me FREE CATALOGUE 



I □ 

| I I Full details of rnodel(s).. 



| NAME.. 



ADDRESS . : - 

Prices and specifications subject to change without prior notice 



407 



ELECTROVALUE 



FAST MAIL ORDER SERVICE 



Mini TRANSISTORS WITH MIGHTY SPECIFICATIONS 

Low cost, Plastic encapsulated, Silicon 

2N42B5 pnp high reverie base-emitter voltage rating. 

BVcbo BVeeo Bvebo all over 35V. fT ■= 7MHz minimum, 

hFE 35 to ISO « Ic = 10mA. Vee(sat) 0-5V max « Jc = 10mA lb = ImA. 
2N-4286 npn high gain hFE = 100 min. « le = lO^A ISO to 600 ■•< le = ImA. 

BVcbo over 30V BVceo over 2SV; fT -■ 260MHi typ "■ Ic = ImA. 
2N4269 pnp high gain hFE = 100 min. .. Ic = lOOfiA 160 min. „i Ic = ImA. 

BVcbo over 60V BVceo over 45V fT = l70MHityp <r Ic = 2mA. 
2N429I pnp large signal high gain hFE = 100 to 300 n Ic - IOOmA Vce = 10V. 

BVcbo over 40V, BVeeo over 30V, Vce(sat) = I 5V max •> Ic = IOOmA, 

lb = I 0mA. 
2N4292 npn UHF. low noise. (T = 570MHi typ S Ic = 2mA Vce ■* 5V, 
hFE — 50 typ. 

SVebo over 30V, Bvceo over ISV, N.f. 6dB max " Ic = ImA, I = IOOMHi. 
2N3794 npn large signal high gain (complementary to 2N429I) 

BVcbo over 40V, BVceo over 20V; hFE = 100 min. ■• Ic = IOOmA. 
All of the above are rated at 500mA max (c, 200mW max «' 25"C. 
Size 0175 x 0090 :-: 0090inhigh. Lead arrangement: in-line. 
B500I POWER type on TO66 siie base, npn high grain. Collector isolated 

from mounting surface {500V insulation). Dissipates 14 3 W max •'• 

Te = 100 Cand Vce = lOV, Vceo(max) - 35V. k(max) = 3A, Ib(max) m I A, 

Tj(max) = I50"C, hFE = 100 co 175 <t Ic = Q5A (yellow selection), 

Vee(sat) = I-2V max W k = I A, lb = 50mA. 
The seven types above are offered at the following low prices: 2NM2B5 to 

2N4292, 2N3794 3/3 each; B500I (yellow) I J/6. 

PEAK SOUND PRODUCTS 

CIR-KIT No. 3 Pack 12/6; adhesive copper 5ft x l/6in or I/I6in 2/-; 
1 00ft x I /Sin or I/I6in 30/-. Perforated board 0-1 in matrix Sin X 3jin, 4>; 
2Jin x 3-iinl/6. 

TRANSISTORISED STERO AMPLIFIER AND PRE-AMP SAB-S 

Complete kit of this very popular amplifier 

16 watts total output £10.10.0 

Power supply kit £3 

i* .» ■" Cabinet £i 

15% DISCOUNT on whole order and post free when purchasing 

an SA8-B! 

EXTRA VALUE IN SEMICONDUCTORS 

Silicon: many types in stock including: 

BCI07, 45V, 3 125-500, 2/9 BCI67, 50V, ft 125-500, 2/6 

BC 108. 20V, ft 1 2S-900. 2/6 BC 1 68, 20V, ft 1 25-900, 2/- 

BC 1 09, 20V, ft 240-900, 2;9 BC169, 20V, ft 240-900, 2/ J 

BCI09 and BCI69 are low noise types, BCI67, SCI6B and BCI69 are plastic. 

Best value for; 

High Power; 2N3055, II5W, 100V, 16/6; 2N3054, 90V, (T 25MHi typ, £1. 

Field Effect: MPFI0S. gm 2 to 6mA/V. »/-; 2N38I9, II'-. 

VHF and fast twitching: BSX20, FT tOOtihti, 4/6, 

High gain: 2N3390, ft 400-1250, 6/-. 

Low Noise: 2N3707, 4/6: 2N339IA 5/6; 2N40S8 (pnp), S/-. 

Sub-Miniature: BC122. 30V, 50mA, 80mW, ISOMHr, I x 1-5 x 2mm. 6/6. 

Low cost: 2N2926, 18V, 120MHz. 2/3 (our colour selection). 

Alto: 2N3702.2N3704.4/-each; BFY50, 5/3. 

Germanium: many types in stock including RF, VHF: NKT603F, 6/; 

NKT6I3F, 3/9: NKT677F, 4/5, 

Low-noise: 2G308; 6/9; 2G309. 7/9; NKT275, 3/8. 

Still running well: 2N1302, 2NI303, 3/6; 2NI304, 2NI305, 4/-; IN 1 306, 

2N1307, 6/-:2N130a, 2NI309, 7/11. 
High Power: NKT403. 14/10; 2N2I47, 16/9; matching, I/- pr. 
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Low cost: IS940, 30V. 75mA, I/-; OA202. 150V, 160mA 2/-: BY238, 850 V, 

500mA 3/9; I N50S4, 800V, I A 4/9; BYZ13, 200V, 6A, 6/9. 
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Germanium diodes: OA47, l/9;OA70, 1/6; t" 

0A95, 1/3. 

SUPER QUALITY NEW RESISTORS 

Carbon film low nois* high scab*: 

Power Range 

I/8W 5% 5'IOto330kn 

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I/4W 10% 4-7fl to I0MQ 

I /2W 5% 4-70 to I0MI1 

IW 10% 4-70 to (OMn 

1/6 per 100 less in complete 100's of one ohmic value 

Please state values required. 

Quality Carbon Skeleton Pre-sets: lOOfl. 250 Q, 5000, IkO, 2k Q, 2-5k(], 

5kO, lOkli, 20k Q, 25k [J, SOkq, (OOkQ. 250kf). SOOkO. 1MQ.2MO, 2-5MO, 

5MQ, I OHO. Available in horizontal or vertical mounting. 1/- each. 

Low cost volume controls: I00O tolOMJJ Hn, SkO to 5MC1 log, 2/3 each. 

Log stereo: lOOkn, 250k [), 500kfi. IMn, 2MO, L.S., 9/-; D.P, sw. 12/6. 

Ceramics: 100, 220, 470, 1,000, 2,200, 4,700pF, 500V, 5d; 01, 02, 0-OSuF. 
50V, 5d. 

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408 



The negative-going edges are used to set a monostable 
multivibrator TR12, TR13 and TR14, whose quasi- 
stable pulse length is preset by VR4 such that it is 
approximately one half-period of the centre "hold" 
frequency, 400Hz, equal to 1 '25ms. 

The monostable output therefore comprises a 1 : 1 
mark/space ratio for this condition, and has an average 
d.c. component after smoothing (R39, C24) of about 
half the battery voltage (7V). Neither Zener diode 
(D10, Dll) conducts, thereby depriving TR16 and 
TR17 of drive; hence, neither throttle relay is energised. 

It can be seen that as the monostable is only influ- 
enced by negative- going edges, and there is only one 
such pulse per cycle, the output dx. level will be 
unchanged as the mark/space ratio of TR5 output 
varies over its full range. 

If, however, the transmitted frequency is raised to 
600Hz ("close throttle") the quasi-stable period of the 
monostable becomes nearly equal to one complete 
period of the signal frequency and TR12 is not con- 
ducting for a high percentage of time. The mono- 
stable output average d.c. component assumes a 
positive voltage, approaching that of the battery, and 
Dll conducts, operating the "throttle close" motion 
relay via TRI7. 

The throttle motor will continue to rotate until the 
frequency is restored to a lower level, or the limit 
switch on the lead screw is operated. If the frequency 
selected is 110Hz then TR12 remains in its stable state 
(conducting) for relatively long periods of time, with an 
average d.c. output voltage of about 1 volt to earth. 
This results in conduction of D10 and operation of the 
"throttle open" relay RLC via TR16. 

The monostable is of a special design which permits 
rapid recharging of the timing capacitor C23 at the 
end of a quasi-stable period. This ensures that the 
monostable is ready to re-enter an accurate quasi - 
stable period with the minimum delay in the stable 
state (about 5 per cent), thus guaranteeing good 
separation between the "hold" and "throttle close" 
signals. 

The "open throttle" discrimination is determined by 
the cut-off condition of TR15 (about 1*5 volts) as a 
result of TR16 base current. The "open throttle" 
frequency need only be low enough to create the cut-off 
condition, any further frequency reduction only 
results in unnecessary chatter of RLC. 

The frequency allocations for throttle control func- 
tions are deliberately made to provide a fail-safe 
feature. It is obviously desirable that the throttle 
should be closed to minimum (tick-over) should the 
transmitter fail or the boat get out of range. Contrary 
to initial expectation, loss of signal does not produce the 
effect of frequency reduction to d.c. conditions, i.e. 
zero frequency. 

The noise level of the super-regenerative circuit rises 
enormously if the carrier is removed, and becomes 
sufficient to trigger the monostable continuously, 
giving a high positive output from TR12. It is wise, 
therefore, to associate this condition with the "throttle 
close" command. 

In a similar manner the random noise pattern gener- 
ated under weak signal conditions results in an approxi- 
mately "average" mark/space ratio of unity on the 
rudder control. As a result the rudder assumes a 
position roughly amidships. The slow speed straight- 
ahead attitude adopted by the vessel was very comfort- 
ing during trials when the transmitter was deliberately 
switched off. 



At this point it will be realised that, had the modu- 
lating frequency of the transmitter been made infinitely 
variable instead of being switched, which could be 
readily achieved by variation of the charging potentials 
of the transmitter multivibrator capacitor, the 
throttle control could have been an independently 
actuated simultaneous position control, in a manner 
similar to that used on the rudder. However, it was 
decided not to do this on the prototype both to preserve 
simplicity, and to explore the possibilities of both 
systems. 

BOARD CONSTRUCTION 

Perforated s.r.b.p. boards were usefl throughout for 
the electronic assemblies and layouts were not found 
to be critical although it is desirable to keep lead 
lengths as short as possible in the 27 MHz portions. 

The receiver panel is actually a peg-board manufac- 
tured from s.r.b.p. and copper laminate (unetched 
printed circuit material) the copper acting as an earth 
plate, being cut away round the plated pegs used for 
connections to components. This is easily done by 
countersinking the -^in peg holes with a i 3 6 in drill 
prior to insertion of the pegs. 

The entire receiver section is mounted on an unetched 
s.r.b.p. card 4in x 4in fitted with isolated pegs, and 
soldering components straight down to the copper 
ground plane as required. The receiver layout is not 
particularly critical provided that lead lengths are kept 
to a minimum and the "earthy" end of certain capa- 
citors are taken to a common point on the ground plane 
as shown. 

So far as the other three assemblies are concerned, 
there is no special need for using copper clad board (as 
shown in the diagrams) and a plain type of s.r.b.p. 
board can be used here if preferred. 

Full layout and wiring details for the boards are 
given in the illustrations (Figs. 4 to 7). 

Next month : Actuator construction and instal- 
lation of drive system and power supply. 



poims nRisinc 



PRACTICAL TRANSISTOR CIRCUITS {April 1968) 
The loudspeaker should be connected between 
C3-r and the — 9V line in the complementary 
symmetry circuit; R6 should be connected between 
C3+ and TR2 base; C2 should be connected in 
parallel with R3. 

SOUND EFFECTS : WIND AND RAIN (April 1968) 
Capacitor numbering in the wiring diagram (Fig. 5) 
should be amended as follows; CI to C7 should 
read C7 to CI 3 in sequence; likewise C8 to CI 3 
should read CI to C6. In the components list Rl 
to R7 inclusive should be 2-7kt3. 

FLUORESCENT CAMPING LIGHT (March 1968) 
Modification for pre-heating the lamp electrodes 
was published in the May 1968 issue. It has been 
found that in this modified circuit (page 375) the 
capacitor C2 is no longer required and should be 

• deleted. The lamp will then give maximum output 
when switch SI is .turned to position 3. 



409 




And some of their applications 
in the electronics industry 



P. A, Dunn, ciba <a.r.l.) ud. 



T:E technique of protecting components by envelop- 
ing them in a "block" or film of moisture-resistant 
material was in use long before the development of the 
present-day potting or casting resins. For many 
years, components such as capacitors have been 
encapsulated in wax or bitumen, while transformers and 
other wound camponents have been impregnated using 
vacuum or dipping methods. 

These processes, however, give very little mechanical 
protection to the components. Moreover, should any 
local overheating occur, thermoplastic materials such as 
wax and bitumen will melt and drain away. Another 
method is to hermetically seal components in a metal 
can, the leads being made through glass-metal seals, 
which are subsequently soldered. This method, how- 
ever, is expensive. 

Epoxy resins, introduced to this country about 18 
years ago, have brought new concepts of design to the 
electrical and electronics industries and the ease with 
which intricate high performance components can 
now be formed with these resins has given a new 
freedom to design engineers. 

APPLICATIONS 

Probably the most well known use of epoxy resins is 
as adhesives and they are widely used as such in the elec- 
tronic and electrical industries. Gramophone rotors 
are bonded, to shafts, ceramic insulators are bonded to 
metal, nickel iron laminations are bonded together to 
form stators, etc. They are also used to bond the lids 
of car batteries and to bond iron powder in the manu- 
facture of iron dust cores. 

A wirewound resistor receiving a coating of epoxy resin by 
the fluidised bed technique 




CIRCUIT BOARDS 

When reinforced with, for example, glass cloth, 
epoxy resins can be formed into structures having a high 
strength-to-weight ratio, excellent electrical properties 
over a wide range of temperatures, great dimensional 
stability under varying conditions, and good chemical 
resistance, etc. Pre-impregnated sheets of epoxy glass 
cloth, pressure moulded to form printed circuit boards, 
are rapidly supplanting conventional s.r.b.p. ("Paxo- 
lin") in high quality equipment. 

CHOICE OF INGREDIENTS 

Chemically the resins are derived from epichior- 
hydrin and diphenylol propane. By varying the 
ingredients and certain phases of the manufacturing 
process a series of resins may be produced ranging from 
rather viscous liquids to hard solids. In the uncured 
state the resins are thermoplastic with poor 
mechanical strength. They are converted into hard, 
tough and substantially infusible materials of high 
molecular weight, by reaction with a suitable hardener. 
A wide range of chemical hardeners may be employed 
and since the hardener takes part in the reaction, the 
properties of the cured product are not only affected by 
the type of resin selected, but also markedly by the type 
of hardener employed. 

Some epoxy resin and hardener mixtures will cure at 
room temperature, while others require processing at 
elevated temperatures. The ratio of hardener to resin 
in each case is fixed within narrow limits and departure 
from the optimum ratio entails loss in performance. 
The choice of hardener can affect the application vis- 
cosity of the mixture, the pot-life and the rate of cure. 
In general, therefore, pot-life and rate of cure can be 
varied only by choice of hardener, and not by change of 
resin : hardener ratio. There are, however, some for- 
mulations in which a small and variable addition of an 
accelerator may be used to adjust the pot-life and cure 
time of a slow acting resin-hardener system. 

FILLING AND COLOURING 

The many combinations and permutations of the 
several basic epoxy resins and the greater number of 
hardeners can be extended by even further modifica- 
tions. The viscosity may be reduced by solvents, 
plasticisers, and diluents. Some diluents and plasti- 
cisers are reactive and can be combined into the final 
cured product. Diluents and plasticisers reduce vis- 
cosity or impart resilience at the expense of strength at 
elevated temperatures. Inert fillers may be added to 
the epoxy resin systems for opacity, cheapness, to 
improve hardness, wear resistance, thermal conduc- 
tivity, electrical and mechanical properties, to increase 
viscosity or reduce the co-efficient of expansion or 
possible exothermic reaction. 



Commonly used fillers are silica, mica, chalk, 
asbestos, glass, and synthetic fibres, etc. Epoxy 
resins can be dyed, pigmented and pastes of colouring 
matter dispersed in liquid epoxy resin are available. 

Although the number of possible combinations of 
resin, hardener, plasticiser, filler, and dyestuff is very 
great and the number of possible amplications is equally 
large, resin formulations for specific purposes are 
commercially available. At the same time, the 
ingredient resins and hardeners are available for those 
who prefer to exercise wider choice or to derive their 
own formulations. 

EPOXY POWDERS 

Although much of the early work with epoxy resins 
in the electrical and electronic industries involved the use 
of liquid epoxy resins, more recent techniques make use 
of the resin systems in powder form. 

Epoxy moulding powders consist essentially of a 
partially cured resin-hardener mixture in powder form. 
In use they are very free-flowing and may be easily 
moulded round delicate inserts, while thin sections of 
resin may be moulded round large metal inserts without 
difficulty. They cure rapidly on the application of heat 
and pressure with negligible after-shrinkage. As with 
other forms of epoxy resin, the absence of volatile 
matter during the curing operation is of particular value. 

The moulding powders have a shelf life of some 
months and are usually stored at temperatures below 
25 degrees C. After processing, they possess high 
insulation strength, excellent dimensional stability, good 
heat resistance, low water absorption, and good 
resistance to tracking. They maintain their dimen- 
sional stability at elevated temperatures and in adverse 
climates. 

Epoxy moulding powders have been widely adopted 
for the fabrication of bobbins, relay bases and con- 
nectors, and for the protection and insulation of 
transformers, silicon diodes, ferrite cores, and metal 
film resistors. 

FLUIDISED BED COATING 

In the fluidised bed coating technique the powder, 
based on an epoxy resin system, is placed in a container 
with a porous base plate. Air is passed through the 
plate which causes the powder to become fluid. The 
component requiring protection is pre-heated and 
placed in the powder which becomes molten with the 
heat and adheres to the component. The time of 



immersion in the powder and the pre-heat temperature 
of the component determines the thickness of the 
coating. Subsequent cure may or may not be required 
depending upon the resin system used. By suitable 
masking techniques, the protective or insulating film 
can be placed where required, as for example, in the 
slots of rotors, eliminating the need for slot liners. The 
absence of solvents, as may be present in normal coating 
systems, leads to the elimination of solvent bubbling 
and solvent entrapment during processing, etc. 

Apart from application by the fluidised bed tech- 
nique, powders can be applied by electrostatic spraying 
techniques or by processes involving the advantages 
of both techniques. 

"E-PAK" TECHNIQUES 

A technique recently introduced to the U.K. and 
particularly applicable to the packaging of diodes and 
transistors uses moulded cases and pre-formed pellets 
of epoxy resin, appropriate in shape and size to the 
component being protected. As supplied the pellets 
are dry, non-toxic, and easy to handle. Cure tempera- 
ture, viscosity, and other physical properties may be 
varied to meet the requirements of productivity. As 
in the case of moulding powders and fluidised bed 
powders, etc., the epoxy pellet in the "E-Pak" process, 
as it is called, is not fully cured and under the influence 
of heat it melts, fills the moulded housing containing 
the components, then sets to form a high strength solid. 

LIQUID RESINS 

In the same way that an electronic component can be 
dipped into a fluidised bed powder, it may be protected 
by dipping into a liquid epoxy resin system. ,In this 
case, however, the component is usually at room tem- 
perature. The liquid epoxy resin system is formulated 
to give a thixotropic characteristic so that the resin will 
not flow from the component during cure. Where the 
specified requirements are not too high, this system 
probably offers the cheapest method of encapsulation. 
It is necessary, however, to take steps to ensure control 
over the thickness of the coating, since, should this 
vary, variable performance under high humidity may 
be obtained and there may also be a tendency for the 
thinner coatings to crack at low temperatures. 

Liquid resin epoxy systems are, however, normally 
employed by pouring the fluid uncured mixtures into 
moulds of metal, plaster, plastic or other material by 
simple gravity casting techniques. Indeed, the term 



(right) Rank Puflin amplifier-transmitter units before and 
after encapsulation 

(below) An epoxy cased transistor from the Multard "Lock- 
fit" range 








"casting" is normally employed to describe the general 
process, although it usually implies the production of an 
insulating or insulated component where the mechanical 
as well as the electrical properties of the material are 
important. 

Potting, or encapsulation, implies the complete 
envelopment and embedment of a component or 
device in a protective mass of the resin, the object being 
not only to insulate, but also to protect the article being 
potted against vibration, shock, dust, ingress of 
moisture, chemical attack, insects, and other 
environmental hazards. It will be appreciated that 
such a technique gives a consistent resin thickness 
around the component being protected. 

The basic casting methods are common to both the 
electronic and heavy electrical industries, but the 
products are usually different. Resins used for encap- 
sulating electronic devices are usually designed to cure 
at low temperatures, for obvious reasons. 

MECHANICAL REQUIREMENTS 

In the case of magnetic materials, which are highly 
sensitive to pressure, such as some high permeability 
steels, it is often necessary to exclude contact with the 
encapsulation resin by making the core external to the 
casting, or by means of certain more specialised 
methods. Metal components can be enclosed within 
the cured epoxy resins, providing that the differences in 
thermal co-efficient of expansion are considered. 

Both thermal contraction and the curing shrinkage 
may be further reduced by extending the resin mixtures 
with inert mineral fillers such as silica, mica, slate, and 
chalk, etc. The use of fillers also reduces possible 
exotherm, increases the thermal conductivity and 
reduces the cost. Fillers are invariably used in the 
production of large castings. 



An automatic dispenser is used by Telegraph Condenser Co. 
for epoxy sealing of capacitors 





Pye of Cambridge use epoxy adhesive* to bond the two 
halves of ferrite pot cores for telephone equipment 



Liquid epoxy resin systems may be used to complete 
the existing closure, made of metal or insulating 
material, with which a component has been surrounded, 
by casting the epoxy resin in the container. For 
example, components may be placed in metal cans and 
sealed with a layer of epoxy resin and by this technique 
the need for relatively expensive sealed outlet bushings 
may be eliminated. 

Certain other liquid epoxy resin systems are specially 
designed for impregnation. The usual technique is 
the straightforward vacuum impregnation used in 
industry, although when considered necessary, vacuum 
may be followed by pressure. 

For the impregnation of windings of electrical 
machines, such as motors, dynamos, and syncros, 
liquid epoxy resin may be employed in the trickle 
impregnation process. Here the wound armatures or 
stators are exposed, while rotating, to a trickle of 
freshly prepared solvent-free epoxy resin mixture, for a 
fixed time at a constant temperature and at an appro- 
priate angle. When the winding is completely filled 
with the epoxy resin, rotation is continued at a con- 
trolled temperature in the horizontal plane until the 
resin has gelled. Heat treatment may follow. 

SOLUTIONS 

Solutions of epoxy resins are also employed for 
impregnation and have advantages over more tra- 
ditional systems. For example, they are used for the 
impregnation and bonding of "C-cores", where their 
adhesive properties are valuable. 

Another major application of epoxy resins is their 
use in surface coatings. Epoxy based primers and 
finishes find wide application for the protection of 
refrigerators, washing machines, and the housings of 
many items of electrical and electronic equipment. «^f 




Impression of United States Apollo 
space station 



FIRST ASTRONAUT 

At the time of writing the sad 
news of the death of Yuri Gargarin 
was announced. He will go down in 
history as the first man in space and 
who marked the starting point of 
manned spaceflight. He was an 
unassuming and pleasant man who 
seemed quite unaffected by the pub- 
licity that his exploit brought him. 
He continued to lead the Russian 
cosmonauts though he did not make 
other spaceflights. This contrasts 
with the American "first men" who 
are no longer connected with space- 
flight. 

RUSSIAN MOON 
PROGRAMME 

It is perhaps appropriate at this 
point to look a little more closely at 
the Russian Moon Programme. It 
has been thought that the general 
trend of Russia's efforts would be on 
the space platform technique. They 
had indicated this on a number of 
occasions when they gave small 
cocktail parties at the Soviet 
Embassy. 

Since the successful remote 
manoeuvring of space vehicles it 
must be a possibility that Soviet tech- 
nology has reached a point where 
they could be very close to the U.S.A. 
in point of time. The rumours of a 
special high thrust booster greater 
than Saturn V were circulating some 
time ago; such a booster could 
have a thrust in excess of I0 9 lbf. 

Possibly this has been once more 
achieved by the same techniques as 
in the past, namely the group or 
cluster method. It could be that a 
circumlunary project is being pre- 
pared in which case, if normal Soviet 
procedure is followed, there will be a 
first such attempt using dogs. It is 
rather significant that nine tracking 
ships came into operation in various 
parts of the world, some with large 
radomes aboard. 

Such a network would be essential 
to any moon attempt which is 
manned. It is known that the astro- 



E5 
By Frank W. Hyde 



nauts are having training for water 
landings, since a circumlunar attempt 
would probably require a landing 
somewhere on the equator. 

VOICE OPERATED DEVICES 

From time to time a certain 
Hungarian, Lazlo Teles, has made 
headlines with his voice operated 
devices. Though some of these led 
to rather embarrassing incidents it 
did not minimise the importance of 
this development of electronic tech- 
niques. 

A number of organisations have 
tackled this problem and now comes 
news from RCA that under contract 
for the American Air Force they have 
under development an advanced 
project for astronauts. The advan- 
tages of such a system are that the 
astronaut would have his hands free 
for tools, cameras, control of a 
personal jet system, etc. while being 
able to instruct other devices. 

The technique of speech recog- 
nition has reached a stage where 
such variations as local dialectal 
differences can be accepted. There 
is a name for this type of recognition. 
The word "Phoneme" indicates the 
smallest part of speech sound that 
can be distinguished. The "f ' in 
"fin" for example is one. 

GROUND STATIONS 

Cable and Wireless Ltd. will be 
setting up two new ground stations 
for public service. Scheduled to be 
in operation by May 1969 they will be 
constructed at Hong Kong and 
Bahrain. A contract has been placed 
with The Marconi Company covering 
the aerial structure and associated 
electronic equipment. The cost will 
be of the order of £2-1 million. The 
total cost to Cable and Wireless for 
this service will be about £3-5 
million. 

These two stations will operate 
through the Intehtat 3 satellites. 
The aerial dishes will be 27 metres in 
diameter and will be mounted on 
18 metre towers. They will be fully 



steerable in order that they may 
follow satellites in any orbit. 

The Hong Kong station will be 
concerned with the satellite over the 
Pacific and will be located on Stanley 
Peninsular. The Bahrain station 
situated at Abu Jajur will operate 
through the other satellite over the 
Indian Ocean. There will be a 
direct service from London to 
Japan, the U.S.A., Hawaii, Aus- 
tralia, Thailand, and the Phillipines. 

It is hoped by 1970 that another 
satellite VK-4 will be launched. A 
design study has been completed. 
There would be a repeat of the 
experiments performed by UK-3 
with three new additions. Three of 
the previous experiments need to be 
repeated for they were spoiled to 
some extent by mutual radio inter- 
ference. All three were in the low 
frequency range of the radio 
spectrum. 

OPTICAL TELESCOPE 
IMPROVEMENTS 

One of the problems in the optical 
field is getting enough area to 
gather the maximum amount of light 
since this determines limits of reso- 
lution. A recent successful system 
has now been developed which 
virtually makes a mirror ten times 
larger. This electronic system called 
the Boyd-Boksenburg Charge Image 
Reader is to be fitted to the new 
Isaac Newton Telescope at Herst- 
monceaux. 

The inventors were Prof. R. L. F. 
Boyd and Dr. A. Boksenburg of the 
Mullard Space Science Laboratory at 
University College London. The 
system has been patented and is on 
the production line. 

Tested on the Isaac Newton 
Telescope it gave an effective mirror 
diameter of 2,500cm. The system 
uses a highly insulated electronic 
storage plate backed by a conducting 
plate on which the optical image is 
directly converted to a charge image 
by photo-emission. The image is 
"read" by the proximity of a vibrating 
probe. The distance between the 
probe and the plate is of the order of 
ten microns. The rapid change of 
capacitance results in an alternating 
current flow which is directly pro- 
portional to the quantity of charge. 
When amplified it results in a picture 
when the probe scans the area. 

The method differs from ordinary 
television scanning in that the image 
is not destroyed during the scan and 
it is therefore possible to build up the 
picture element till it reaches a 
suitable value to be useful. 

There are many great advantages 
to be derived from this device. A 
photographic image may take hours 
to expose where this method takes 
minutes, and in addition there is no 
grain to mar detail. Moreover the 
direct readout eliminates the pro- 
cessing of film and the attendant 
techniques, and not least avoids the 
uncertainty of the success of the 
exposure. 



41 3 




A LIGHT OPERATED 




By A. FOORD 



There are frequent occasions when one would like to 
trigger some apparatus into operation without 
being present to operate it oneself. Examples of some 
applications are burglar alarms, counting circuits, 
photography, and so on. 

In photography, a birdwatcher is a special case. All 
too often the bird, or indeed any animal, can be heard, 
but one has to wait patiently for some time before it 
will show its face. In the time it takes to set up a 
camera to photograph the subject,- it could have 
vanished as unexpectedly as it appeared. 

What is required, then, is some device that could be 
set up in the field ready to trigger the camera without 
undue loss of time. Such a device is described here 
and was designed to fulfil the following requirements, 
bearing in mind the use of the photo-electric principle 
of breaking a light beam. 

1. To respond to the fast or slow movements of 
birds or animals. 

2. To be unaffected by very slowly changing external 
light, such as daylight. 

3. The distance between the light source and the 
triggering unit had to be as great as possible to 
avoid the animal scenting the photographer. 

4. The unit should be lightweight, portable, and have 
low power consumption. 




CAMERA 



MOTE 
RELEASE 



Fig. I. Diagram of the camera trigger set-up 

414 



5. As most animals are sensitive to white light but 
not to red, a dark red filter was placed over the 
light source to render the beam inconspicuous. 

SHADOW TRIGGER 

The system used is illustrated in the block diagram 
Fig. 1 . The complete circuit is given in Fig. 2. The 
drop in light intensity on the photocell, caused by the 
shadow of the subject, is used to trigger a monostablej 
multivibrator. A low power lens, such as found 
a watchmaker's eyeglass, was found to be suitable fc 
directing the light onto the photocell, in this unit 
phototransistor TR1. The eyeglass can be obtair 
quite easily through large well stocked toolmerchanj 

Transistors TR2 and TR3 comprise the mi 
vibrator, and TR4 operates the relay. 

Consider at some instant that TR1 is illuminated. 
When the uni* is switched on TR3 will conduct, since 
its base is returned via R7 to the negative rail. Thus 
TR3 collector-emitter voltage will be almost zero, and 
TR2 and TR4 will be cut off. The circuit will remain 
in this state indefinitely unless compelled to change by 
an externally applied signal. If the light beam is cut, 
a negative going pulse will be applied to TR2 base, 
making TR2 conduct and produce a positive pulse at 
its collector. This pulse is applied via C2 to the base of 
TR3, cutting it off. A negative pulse appears at TR3 
collector and is applied to TR4 base; TR4 conducts to 
pull in the relay. 

The circuit is now in the second of its two possible 
states: TR2 conducting, TR3 cut off, but will not remain 
in this state for long because C2 (which was charged up. 
when it conducted the pulse from TR2 to TR3) imme- 
diately begins to discharge through R7 and the output 
circuit of TR2. As C2 discharges, TR3 base becomes 
less positive until TR3 conducts again. The circuit is 
now back in the stable state. 

In brief, when the beam is interrupted, the unit 
changes from its stable state (TR3 conducting; TR2, 
TR4 cut off) to an unstable state (TR3 cut off; TR2, 
TR4 conducting) and operates the relay. The duration 
of the latter condition is given by / — 0-69i? 7 C-> seconds. 



COMPONENTS 



Resistors 


FU 


I8kfl 


R2 


3-9kH 


R3 


llOkil 


R4 


I50kii 


R5 


3-9k£l 


R6 


iska 


R7 


39kQ 


R8 


3-9kfl 


R? 


47kfl 



All 10%, i watt carbon 
Capacitors 

Ci 8^ elect. 15V 

CI 8^F elect. 15V 

C3 0'CW2^.F paper or polyester 

Transistors 

TRI OCP7I (phototransistor) 
TR2, 3, 4 OC20I (3 off) 



Diodes 

DI, 2, 3 



OA8I (3 off) 



Relay 

RLA 



I85Q 6V type MH2 (Keyswitch Relays) 



Miscellaneous 

BY I Battery 6 to 12V 

Ml Meter 0-1- 5mA f.s.d. 

JKI, PLI Jack with two break contacts and plug 

Sockets for wander plugs (2 off) 

SI Single-pole, on/off, toggle switch 

Light source {.bicycle lamp) 

Red fifter (llford No. 608) 

Component tagboard, 10 pairs of tags 

Diecast box 6|ln X 4Jin x 2£in or similar 

Watchmaker's eyeglass 

Battery retainer and clips 

Insulation board, s.r.b.p., 41 n x 3 in 



For the values shown the relay hold-in time is about 
0-2 seconds. If this time is not sufficient (in any par- 
ticular case) it may be increased by increasing the 
value of C2. 

It is usually desirable for the unit to operate with the 
minimum of time lag, the addition of C3 gives appreci- 
able feedback at high frequencies, and ensures that the 




The complete tight 

operated camera trigger control 



rectangular pulses generated at the collectors of TR2 
and TR3 are sharp edged, so that the monostable 
changes state rapidly. 

SIMPLE TO MAKE 

The diode Dl may be any small signal type, while 
D3 prevents the high back e.m.f. from the collapsing 
magnetic field of the relay from damaging TR4. D2 
is inserted to prevent damage if the battery connections 
are accidentally reversed. Relay RLA could be any 
6V type requiring up to 30mA to operate it (see com- 
ponents list). 

The construction used for the unit would vary 
according to the needs of the constructor; a diecast 
box is ideal for this to exclude unwanted light. Fig. 3 
shows the tagboard wiring and tagboard component 
positions. The photograph shows the layout in the 
box, this will depend to a large extent on the focal 
length of the lens used. The one in the prototype has 
a 2in focal length. 

For a lens of short focal length the phototransistor 
can be mounted on the back of the box as shown, with 
the lens mounted in a hole in the box lid. The trigger 
unit is connected to one of the remote camera releases 
available commercially, these usually consist of a 
solenoid released plunger, operated from a battery 
when a contact is made. 



R5> >R7 

3-9kA> C2 >39m 

8>iF 



R3 D3 

■3-9ka 0AS1 



H1 R1 \£S/0CP71 '^ VlV 0C2Ol ylV 0C20l R9 V^VoC 

0T0 1-5i»A 16kA ^^ ^^ R6 ^^ 4-7kA ^^ 




RLA1 




>R4 

>i5om 



R6 

i — W — i 

»5kfl 



C3 
0-002j>F 



BY1 

&V TO 12V | 



TO REMOTE 
RELEASE 



DZ| J ^0A81 



w 



V 



Fig. 2. Complete circuit of the trigger unit 




415 




TO TO BY1 NEGATIVE 
SI AND RLA COIL 




Fig. 3. Component layout and wiring of the tag board 
in the trigger unit 



The meter Ml in series with TR1 is for setting up, 
and is externally connected via a jack JK1, with break 
contacts to short the jack when not in use. 

The phototransistor is mounted as shown in the 
photograph so that the emitter junction is facing the 
lens. This can be seen through the glass envelope and 
recognised as the side of the base (square piece) with 
the largest "blob". 

SETTING UP PROCEDURE 

Using an ordinary bicycle front lamp, reliable opera- 
tion can be achieved with a beam length of over 40ft 
without the filter, and 20ft with the filter. The light 
source and trigger unit are mounted on camera tripods. 
The light source should not be run from a.c. supplies, 
otherwise unreliable operation will result. 

Point the light source in the required direction and 
switch on. Arrange the trigger unit in the path of the 
light beam and switch on; the leads to the remote 
release should not be connected at this time. 

Swing the trigger unit vertically and horizontally 
until Ml reads a maximum. Lock the trigger unit in 
this position; the light is now focused on TR1. For 
reliable operation Ml should read at least 0-5mA. 
There is no point in providing enough light to give more 
than 1mA current, so the intensity of the light source 
should be adjusted according to the range required. 

Remove the meter from JK1. Now, by passing the 
hand through the light beam you should hear the click 
of the relay. The output sockets can be temporarily 
connected to an ohmmeter, or a series bulb and battery, 
to ascertain that the relay is actually switching. If all 
is in order, connect the remote release to the trigger 
unit and all is ready for photographing, provided the 
camera is aimed at the light beam, where the subject 
will be. -Jc 




Interior view of the trigger unit showing layout of ail components and interconnecting 
wires. Note the positioning of the phototransistor must line up with the lens mounted on 
the lid. 



416 



tnKyxgte©™© 




for the 
EXPERIMENTER 

By M.L. Michaelis M.A. 




8— STRACE RADIATION METER (Continued) 



Last month the ratemelcr module of the STRACE radia- 
tion meter unit, was described. Before going on to 
consider the other sub units which make up the complete 
unit, a few remarks concerning chart recording will be 
appropriate. 

CHART RECORDING 

The circuit of Fig. 7.1 illustrates all essential features of 
a modern ratemeter possessing high efficiency and excellent 
stability with respect to time and temperature. This 
circuit is eminently suitable for chart recording. 



f ** 




*0 

1 


4?. 


1 - £ 


iitflflllMi- ^D 


V 


A? - 


* i. • -■ ;! 





One of the pip generator modules of the STRACE Radiation 
Meter 



The recommended chart recorder is the model "Metra- 
watt Multiscript 3" obtainable from" Messrs. Smiths 
Electric Clocks Ltd, This is a precision multimeter, which 
may also be used as such and possesses a scale and pointer 
in the usual arrangement. The pointer is a sharp knife- 
edge type and hovers above special pressure-sensitive 
waxed paper obtainable in rolls from the same makers. 
This paper carries the same scales across its width, and is 
driven forwards by a small mains synchronous motor, at 
a rate selectable with an internal lever. The motor at the 
same time drives a strirrup via a cam, causing the stirrup 
to drop onto the pointer once every two seconds. The 
knife-edge thereby strikes the waxed paper and makes a 
black mark. For chart-recording with the STRACE . 
equipment, the Multiscript 3 should hfe set to the 1mA 
f.s.d. range, and the paper speed lever, to' 20mm/hour. 

Chart recording enormously enhances the scope of a 
ratemeter, for two important reasons. Firstly, the 
gradual decay of the activity of samples with short half- 
lives is thereby traced directly. It would be most incon- 
venient to sit and watch the panel meter for such purposes. 
Secondly, even when measuring long-life samples with 
insignificant decay over the time of recording, it is readily 
possible to draw a mean straight line through the residual 
random fluctuations of the recording. This leads to an 
effective statistical accuracy considerably better than the 
nominal design figure of 5 per cent for panel meter read- 
ings. In other words, chart recording brings the overall 
accuracy to a figure at least as good as the read-off accuracy 
of the chart recorder itself. .* 

The long-term stability of the circuit of Fig. 7.1, when 
properly adjusted, is so good that the recordings are dead 
straight lines for days on end with no input pulses, or 
with a fixed input frequency from a crystal-controlled 
pulse generator, even if ambient temperatures and mains 
voltage fluctuate in the meantime. This zero-point 
stability is of course essential for reliable chart recording 
in the 2 per cent accuracy class. 



ADJUSTMENTS 

A source of standard pulse frequencies is required. 
These may be obtained from a crystal-controlled generator, 
or from any simple pulse generator (e.^. the Heathktt IG 82) 
which is tuned accurately to successive harmonics of the 
50Hz mains by observing Lissajou figures on an oscillo- 
scope. 



PIP VOLUME CONTROLS 



SUBSIDIARY POWER 
SUPPLY FOR PROGRAMME 
CONTROL MODULE 



COMMON AUDIO AMPLIFIER 

IX TRANSFORMERS 
E.H.T. TRANSFORMER 




The STRACE Radiation Meter 



First of all, switch to Range 1 and adjust VR3 for 10 per 
cent f.s.d. on meter and chart recorder. Then back-off 
both devices with their mechanical pointer setting screws, 
to give zero scale readings. 

Now switch to range 4 and tune the pulse generator to 
the third harmonic of the mains (150 Hz), Adjust VR5 to 
obtain meter reading 9,000 c.p.m. Then retune to 50Hz 
and correct with VR7, if necessary, to read exactly 
3,000 c.p.m. 

Repeat adjustment of VR5 and VR7 alternately until 
no further improvement. 

Switch to range 3. Adjust VR6 for zero scale reading 



with no input. Switch to range I and connect-up a 
G.M. counter detector unit without sample, i.e. counting 
solely the cosmic radiation background of about 40 c.p.m. 
Determine the true c.p.m. value by counting the pips in 
the loudspeaker (see below) and timing with a stopclock 
or watch with seconds hand. Adjust VR4 for correct 
reading. Wait at least 5 minutes between successive 
adjustments of VR4. Finally, feed positive pulses of 
2V amplitude to PL2, or 5V amplitude to PL3, using 
pulse generator and oscilloscope. Adjust VR2 such that 
pulse expander just triggers, i.e. pips just audible in the 
loudspeaker. 




INPUT PULSES FROM 
RATEHETER MQ0ULE, 
TA6 E (FtG 7,1) 



ALL OTHER COMPONENT 
VALUES UNCHANGED 



INPUT TO AUDIO 
AMPLIFIER MODULE TAG A 



Vmf CHANNEL I 
PIP VOLUME 
(tUtt) 



Fig. 8.1. STRACE RADIATION METER: circuit diagram of the pip generator module 



41« 




The audio amplifier module of the STRACE Radiation Meter 



Now to resume discussion of the remaining circuitry of the 
radiation meter. 

THE PIP GENERATORS 

Fig. 8.1 shows the full circuit of the pip generator 
module. The layout and semiconductor types are not 
critical, and it is possible to accommodate this circuit on 
a 2*5in x 3-75in piece of Veroboard. 

We saw that the pulse integration time is 160 seconds 
(40t*F x 4 megohm) on ranges 1 and 2, so that individual 
pulses produce little or no visible change in the meter 
reading, and the final meter reading is not reached until 
about 10 minues have elapsed. Some means of getting a 
rough immediate idea of the pulse rate is therefore 
essential, for selecting an appropriate range and for check- 
ing that the detectors are working correctly. This func- 
tion is achieved acoustically, by making each pulse from 
the detector produce an audible pip in a small loud- 
speaker. 

The STRACE radiation meter possesses two identical 
ratemeter channels according to Fig. 7.1, and thus also 
two pip generators according to Fig. 8.1. The latter 
differ only in the pitch of the pips they produce, so that 
the two channels can be distinguished when sounding 



Fig. 8 J. STRACE RADI- 
ATION METER: Cir- 
cuit diagram of the 
power suppy section 



INPUT FROM 
VOLUKE CONTROL 
NfTWOflK 



<$>IH.7 
OUTPUT TO TAPS 
RECORDER AW/ OR 
TELEMtTltr TRAN5HITTER 



PANEL 
LOUDSPEAKER 

iioon 



Fig. 8.2. STRACE RADIATION METER: 
of the audio amplifier module 



Circuit diagram 



simultaneously in the loudspeaker. Channel 1 sounds 
400Hz pips, whilst channel 2 sounds 1kHz pips. The 
components C9 and R12 in the respective pip generators 
are selected accordingly, and VR4,6 adjusted to give the 
respective pip pitches. 

SINEWAVE OSCILLATOR 

The pump pulses from the ratemeter are also fed out 
via R18 of Fig. 7.1 to the pulse inverter TR1 of Fig. 8.1. 
This triggers another expander, which produces the much 
longer gate pulse for generating a pip of audible duration. 
This gate pulse drives the modulator TR4, which keys an 
RC sinewave oscillator of the suppressed-harmonic multi- 
vibrator type. This circuit keys very neatly to give 
accurate bursts of sinewave oscillation of about 20 cycles 
per burst. 

continued on page 421 




MAIMS INPUT 
LIVE 



m — ' 0000 ^— o-o-rno- 



0N/0FT 1 



EARTH 



M 



o-oSjjf^F ^p, 

500V AC. I 

» Tfffffl? 



TO AMPLIFIERS 

AND PULSE CIRCUITS 



MAINS 



MAINS 



*- LIVE 

6-3V A.C. SWITCH VOLTAGE 
TO'EHT POWER" CONTACT 



„ TO PROGRAMME 
r CONTROL CIRCUIT 



+450V 

CHANNEL 1 




E.H.T. FOR 
► GEIGER-MULLER 
RADIATION DETECTORS 



DO 0-05uF 
500V AX. 



419 




(LDRqELDG^nDTT 



IN THIS feature we hope, from time to time, to be able -to 
publish suggestions submitted by some of our readers on the 
possible improvement of projects previously described in 
PRACTICAL ELECTRONICS; short contributions on other subjects 
may be included. The aim is not to find fault or undermine the 
abilities or knowledge of our contributors. It may well be that the 
original article is par exellence but it could be improved or adapted 
to suit individual requirements. The views expressed by readers 
are not necessarily those of the Editor. 

ADDING AN "X" AMPLIFIER AND SCRIBING THE GRATICULE 



To Y 



To Sla 

tfipcr 




Modified circuit with additional component values given 



Here is one suggestion for putting the spare valve to 
good use in the Investigator Oscilloscope (July 
1967). Rather than add more valves the unused V4b 
is wired so that the timebase can be switched to bring in 
an X-amplifier in its place, using a 7-pole 2-way 
switch. 

The circuit is simplified by the omission of the time 
base range and attenuator switches and several other 
components. The new X-amplifier is identical to the 
Y-amplifier and the setting of VR6 should be deter- 
mined by trial and error. 

Constructors wishing to build this unit are referred 
to The Oscilloscope and its Applications (March and 
April 1967) which covers the measurements that be 
undertaken using an X-amplifier instead of a timebase 
circuit. 

And now another small addition to the Investigator 
Oscilloscope which might prove useful. When 
the lines on the perspex graticule are being scribed it 
will improve the accuracy of the reading taken if lines 
are scribed on both sides of the perspex. 

420 



This acts in the same way as the Mirror Scale on 
some of the more expensive multimeters, that is when 
the pointer and its image in the mirror coincide, then 
the eye is directly above the pointer and the reading 
is the most accurate in this position. The point where 
the image and pointer coincide is known as the position 
of no parallax. It is important to be directly above the 
reading to be taken because if the meter is being read 
from an extreme angle a considerable error is incurred. 

To apply this method to the Oscilloscope the head 
should be moved about until the lines on the outside 
of the graticule coincide with those on the inside. 
Thus more accurate readings can be taken. 

It might be found that the lines on the outside of 
the graticule may lose their layer of black wax with 
constant use so it may be advantageous to place 
another piece of perspex in the front of the graticule 
to preserve the lines. 

I. W. Berry, 
Huddersfield. 



WHITE NOISE GENERATORS 

Readers may be interested in the following White 
Noise Generator circuits, having seen the article 
published in the January 1968 issue, The circuit in 
Fig. 1 was derived from the Bonanza Board Simple 
Pre-amplifier and Treble Booster described in the 
March 1966 issue. The components shown in dotted 
lines are those omitted from the original circuit, also 
the printed circuit board for the noise generator and the 
pre-amplifier are identical. All that is necessary to 
convert the pre-amplifier into a noise generator is the 
replacement of Dl, the base-emitter bias diode, by a 
device having a poor reverse resistance in the region of 
5 to 10 kilohms. Also it is important to omit the 
original diode bypass capacitor as this attenuates the 
high frequency output. « 

-AA/^ o 




Fig, I. 



~£ — f 

I, »f 



>130kfl 



r f— If 



AA/ *■- 

4 . 7 kA 2O0-250V 

1(i F 



OUTPUT 



6BR7 




Fig. 2. 

The circuit in Fig. 2 relies on the movement of 
heavy particles due to the ionised gas in a miniature 
neon indicator to produce white noise. The neon 
used may be of the type used as mains warning in- 
dicators provided that it has no integral series resistor. 
If construction of this circuit is contemplated it must 
be remembered that neons tend to be susceptible to 
mechanical shock when used in this application, and 
thus the unit gives best results if fitted with anti- 
vibration mountings. 

S. A. Hardy, 
Chippenham, Wiltshire. 



NUCLEONICS FOR THE EXPERIMENTER 

continued from page 419 

Adjust VR3,5 such that triggering is secure. Then adjust 
VB.4,6 to give correct pitch of the pips. If the oscillator 
bursts into continuous oscillation before correct pitch 
can be reached with VR4,6, judiciously increase the value 
of C9. Continuous oscillation also results if VR.3,5 is 
turned too far towards R4, but this can be distinguished 
by its staccato form, as compared to a pure sinewave squeak 
if too low a value of C9 is the cause. 

THE AUDIO AMPLIFIER 

Fig. 8.2 shows the circuit of the common audio amplifier, 
using three readily available germanium transistors. 
TR1 is a driver stage for the series-push-pull output stage 
TR2 3 

This simple circuit develops about 75mW output 
power and is thoroughly recommendable for monitoring 
purposes in general electronic equipment. Layout is 
again quite uncritical, and accommodation on a piece of 
2- Sin x 3 -7 Sin Veroboard, or even smaller, is a simple 
matter. 

If a 1 OX) ohm speaker is unobtainable, any other im- 
pedance may be fed from a suitable matching transformer 
(e.g. about 4-5:1 ratio step-down for a 5 ohm speaker). 
The exact ratio for the transformer is not critical, and a 
sub-miniature component is satisfactory. 

Returning to Fig. 8.1, it is seen that the outputs of the 
pip generators are fed via respective front panel volume 
controls to the common audio amplifier. Either channel 
may thus be sounded alone at any desired volume, or both 
may be sounded together, whereby distinction is still 
possible by virtue of the different pitches. Both volume 
controls may be turned to zero when running the equip- 
ment on automatic chart recordings overnight, and noise 
is thereby undesirable. , 

It is of course equally possible to construct a radiation 
meter with only one ratemeter module, with or without a 
pip generator and audio amplifier. Or a single pip 
generator may be provided, which can be switched to 
either ratemeter module at will. 

POWER SUPPLIES 

Fig. 8-3 shows the power supply circuit providing all 
voltages for the circuits of Figs. 7.1, 8.1, and 8.2. The 
bridge rectifier and smoothing circuits with Zener diode 
stabilisation associated with TR1 are conventional. 

D9 is a 15V power Zener diode and D10 a 12V power 
Zener diode. Both are rated for at least 750mW dissipa- 
tion without cooling fin. The 250V winding of TR2 feeds 
a voltage doubler circuit for the e.h.t. supply for the 
specified G.M. counter detectors (450V stabilised). Dll 
and D12 may be any standard television silicon h.t. 
rectifier or other mains type. t . 

VI is a Noval-based Telefunken valve containing four 
miniature neon stabiliser sections of 125V running voltage 
each. Four separate neons or Zener diodes of equivalent 
rating may be used in series as alternatives. 

The a.c. input to the e.h.t. rectifier circuit is switched via 
an extra contact on the scintillation spectrometer switch. 
Thus the G.M. counter detectors are automatically 
switched off when power is switched on to the scintillation 
detector/kick-sorter amplifier unit, and vice versa. The 
pulse cables of both types of detector units may be left 
connected to the radiation meter. 

This completes our survey of the pulse processing 
circuits employed in a very typical analogue radiation 
meter. We have seen that two parallel channels are here 
provided. Professional equipments may use much greater 
numbers of parallel channels. These can be run on 
entirely independent experiments, but more commonly 
some form of coordination for a single composite experi- 
ment is required, since this is the only real justification for 
including more than one counting channel in a single 
equipment. The channel coordinating circuits are known 
as the programme control section of nucleonic equipment. 

Next month: Programme control circuits. 



421 



Transistor Amplifier 





By A. Foord 



NEGATIVE 
FEEDBACK 



Last month's article gave an outline of the theory of 
negative feedback principles. Continuing now 
with this subject, the virtual earth amplifier is described 
in relation to feedback; later on, negative feedback 
will be shown to have an influence in designing tone 
control networks. 

VIRTUAL EARTH AMPLIFIER 

For a "virtual earth" amplifier, an inverting amplifier 
is used and the output taken directly back to the input 
(see Fig. 5.1) via the feedback resistor R2. The open 
loop gain of the amplifier is A where the bar indicates 
phase shift of 180 degrees. R3 represents the input 
impedance of the amplifier; R2 and Rl determine the 
gain with, feedback. 

In the analysis we assume that R2 and Rl do not 
load the output of the amplifier. Since the gain A is 
large, the voltage Kat point /(will be small {Vol A) for 
practical values of V Q , so this point is often called a 
"virtual earth". The larger is A the smaller will be V. 
Taking into account the shunting effect of R3 and the 
finite gain for A, the overall actual closed loop gain 



V x R t 



1 



1 t R + R% 



where R is R a and R t in parallel 

R1 + R3 

If A is large this simplifies to 

Vo 

Vi 



Ideal closed loop gain G = ~ = — -~ 

R\ 



Provided A is large the gain is determined by the feed- 
back resistors; taking a practical example we can 
compare the results between the actual and ideal 
formulae. 

If R x = 1 kO R s = 10 kO R 3 = 10 kfl A = 50 

(a) Using the accurate formula: 



R = 



„**** =~ = 0-91 kilohms 
Mi -J- /C 3 II 



G' = - 10 X 



1 



1 + 



10-91 



= — 8 times 



50 x 0-91 
= I8dB 

(b) Using the ideal formula: 

G = - 10 times = 20dB 

422 



We aimed for a gain of 20dB and obtained 18dB, so 
that when A is only 5 times the required closed loop 
gain and R 3 is only ten times R lt the error in using the 
ideal formula is small, 2dB in this case. If A had been 
larger (say 100) the error would have been smaller, as we 
would expect from our theory on feedback in general. 

It can be shown that the impedance at the virtual 
earth point A is given by: 



If R 2 - 10 kilohms and A = 50 

10* 
^a = -sk = 200 ohms 
50 

This low impedance at this point is another reason 
for calling this a "virtual earth". If we consider the 
complete amplifier including Rl, then 

Z\. — R\ 

The output impedance of the amplifier (Fig. 5.2) 
without feedback is represented by Z' and could be of 
the order of 100 ohms if the last stage of the amplifier is 
an emitter follower. The output impedance with 
feedback is given by 

Z - y x ^ = 20 ohms 
A Rx 

The output impedance is reduced. The frequency 
response is improved by a factor of ARJR Z at each end. 
If the amplifier had its upper 3dB point at 6kHz then, 
if as before, A = 50, J?, = 1,000, R t = 10,000 the 3dB 
down point is improved by (50 x 1)/10 or 5 times, to 
become 30kHz. Similarly at the low end, the lower 3dB 
down point might be extended from 200Hz to 40Hz 
(Fig. 5.3). 



SHUNT LOCAL FEEDBACK 

The simplest method of applying this feedback is 
around a single common emitter stage, see Fig. 5.4. 
As one might expect, the effect of decreasing R 2 is to 
decrease the gain and increase the bandwidth of the 
overall response (Fig. 5.5). 

It is desirable to make Ri, high in order to increase the 
open loop gain of the amplifier, but unfortunately 
this means that Ri, will be loaded by the next stage, so 
that it is not possible to predict closed loop gain by the 
above formula. By feeding J?l into an emitter follower, 
a better arrangement is possible, see Fig. 5.6a. 



K2 



r^V-Tn^^ 



.83 




gain d8 



h 



op«n loop gain 



closed loop gain 




frtqtuncy ~ 



Fig. 5./. Basic con- 
figuration to illustrate the 
"virtual earth" amplifier 



Fig. 5.2. Output 

impedance without feed- 
bock is Z'n 



Fig. S3. Extended fre- 
quency response by using 
negative feedback 




470 p A 



(ZfflA 



-I8V 



, gain 



ditrtastrtq 
RZ 



^ 



frequency 



Fig. 5.4. Simplest form of 
negative feedback through 
R2, which is also used to 
bias the base 



Fig. 5.5. Effect of 
decreasing the value of 
R2 in Fig. SA to 
increase bandwidth 




The collector load of TR1 is no longer loaded by R2, 
the output impedance of the amplifier is already low 
and is further decreased by the feedback, and R3 will 
not shunt the virtual earth point to any extent. The 
open loop gain Vol V was about 300 times, which agrees 
with the similar figure obtained when using this 
amplifier previously for series local feedback. 
j> 39 

Closed loop gain =^ = 5-5=10 times = 20dB 
Hi 3 - 9 

Zi = 3,900 
Z = 10 ohms 
Maximum output ■= 500mV r.m.s. into lkii 

Without the capacitor across R2, the amplifier has a 
bandwidth of 60kHz; with 180pF across R2 the band- 
width is restricted to about 22kHz (see Fig. 5.6b). 

Since this amplifier needs to be fed from a source 
impedance low in comparison with Rl, it can be fed 
either from an emitter follower or from the output of a 
similar circuit. These amplifiers can therefore be 
cascaded without interaction, the maximum output of 
500mV into 1 kilohm is governed by the emitter current 
ofTR2. 

For a similar stage which presented a load of 
3-9 kilohms a larger signal could be handled. If this 
amplifier needed to feed 500mV r.m.s. into a power 
amplifier which actually had a low impedance of the 
order of 1 kilohm, it might be better to reduce the 
emitter resistor of TR2 from 4-7kn to, say, 2-2kfl so 
that there was no danger of the amplifier limiting. 

The polarity of the input capacitor assumes that the 
amplifier is fed from a similar amplifier or an emitter 
follower. 



Fig. 5.6a. To avoid heavy loading of the amplifier 
stage an emitter follower Is used 



dB 




















20 




















15 














Without 
JBOpF 


10 




With 1 


80s? 














? 








































frtqiitfley (kHr) 



100 



Fig. 5.6b. The feedback resistor R2 can be shunted 
by a capacitor to reduce bandwidth 




Fig. 5.7. Three inputs ore mixed into the "virtual 
earth" point of the amplifier 



423 




Fig. 5,8. A detailed circuit of the 3-channel mixer, each 
input being "buffered" from the others by an emitter 
follower 



ZZtiF 



BOOST 
BASS 
VR2 



I T v VV-r^ 




Fig. 5.9. A typical example of the Baxandail type of feed- 
back tone control circuit for treble and bass boost and cut 




frequtncy(Hz) 



JOOO 



(0,000 



_BOOST 



— vy\ — | 



Fig. 5,11. 

Treble 

control 



m 






{^ 



a 



Fig. 5.12. Treble flat 



r4H 



Fig. 5.13. Treble boost Fig. 5.14. Treble 
cut 






Fig. 5. 1 5. Bass control 



VRZ 



W2 r4 cz P\AA- 



F/g. 5.16. Bass flat 



cz 



M 



H2 



vrz ^AAA-| 



c^ 



Fig. 5.17. Bass boost 



VRZ 



Fig. 5.10. Upper and lower limits of frequency response 
given by the Baxandail circuit 



Fig. 5. IB. Bass cut 

Figs. 5.11 to 5.18. This series of diagrams shows the 
maximum, minimum and "flat" conditions of the 
Baxandail circuit 



424 



MIXING 

Mixing can be achieved by adding extra inputs at the 
"virtual earth" point, Fig. 5.7. 

If Rl - R2 = R3 = R. This becomes 

A practical audio mixing unit could be made up in this 
fashion (Fig. 5.8) for three or more inputs. 

Input impedance == 8kO 

Maximum gain = 10 times = 20dB 

Maximum output = 500mV 

Frequency response 20Hz to 20kHz, ±3dB, 

Each parallel input stage is identical. 

FEEDBACK TONE CONTROLS 

The virtual earth arrangement can be used with 
feedback and input networks that are frequency 
selective, providing tone controls of the well known 
Baxandall type (see Fig. 5.9). The performance of this 
circuit is given in Fig. 5.10, and was measured with the 
gain control at maximum, so that the tone controls 
were effectively fed directly from the previous stage, 
which had an output impedance of 250 ohms. 

With the volume control at a lower level, the source 
impedance would be slightly higher (up to a maximum 
of 5k Q) but this would not effect the response curves by 
more than a couple of dB or so, since the tone control 
network is made a high impedance network. 

The 2N 1309 was used here so that the open loop gain 
without feedback extended well outside the audio band. 
An OC75 (which has a lower cut-off frequency) could be 
used here, but the response on maximum treble boost 
might not be as great. 

Slightly more bass boost can be obtained by reducing 
the 47 kilohm resistors to 22 kilohms. Performance: 
When no boost or cut is applied ±3dB, 20Hz-20kHz. 
Bass boost 12dB at 20Hz; cut 19dB at 20Hz. Treble 
boost 19dB at 20kHz; cut 19dB at 20kHz. 

The overall gain is about unity at mid-band and will 
give a maximum output of 500rnV into 1 kilohm. 
The circuit has been broken down into eight con- 
figurations in Figs. 5.11 to 5.18. Taking the treble 
section (Fig. 5.11) this can be divided into three 
conditions: flat (Fig. 5.12) ; boost (Fig. 5.13); cut 
(Fig. 5.14). 

Secondly, the bass control in Fig. 5.15 gives equal 
source and feedback impedances (and hence unity 
gain) in the flat condition, Fig, 5.16. Feedback is 
reduced at low frequencies to give bass boost, Fig. 5.17. 
In the bass cut condition the input network increases 
in impedance from 1kHz towards 20Hz, and overall 
gain is reduced below unity, Fig. 5.18. 

To ensure that the tone controls are not overloaded 
on peaks, it is preferable to place the volume control as 
early in the circuit as possible, so that the tone controls 
are operated at a low level, see Fig. 5.19. 

VOLTAGE OUTPUT, SERIES INPUT 
NEGATIVE FEEDBACK 

Apart from the virtual earth arrangement, there is 
another method of applying negative feedback over two 
stages: the voltage output, series input arrangement. 

In this case (Fig. 5.20) the resistor R2 enables a 
signal proportional to load voltage to be fed back, 




Magnetic or ceramic 

pick-up 



WUJHE 

T CONTROL 

VampHfierrcr COffTROlS 
equalisation for 
magnetic pick-uo,or 
High to low 'impedance 
matching unit lor 
ceramic pick-up 

Fig. 5.19. Volume control Is 
inserted before tone controls so 
that boost condition is not 
distorted 




Fig. 5.20. Voltage output, series input 
negative feedback 



j~<$r=$> 



'R2 



Fig. 5.2 I. Theoretical 

equivalent of Fig. 5.20 



-wv 




Fig. 5.22. Practical circuit of amplifier with voltage 
output, series input negative feedback 



425 




• 6.8 
. kfl 



TW^ TR2 

^ihS 3D 



frequency (kHz) 



Fig. 5.23. Frequency response of circuit in Fig. 5.22 
with and without shunt capacitor 



VI 


<J& 














so 


s,_ 




Open to ob coin . 












f 




















VI 






















is 






















<n 




Id 


















T0jjS s % 


^y frequency respons 


I j 
































?' r < 














































<5 

10 












































5 
























1 




-i 


















(00 



zm 



tOk 



frequency (Hz) 

Fig. S.2S. Ideal tape replay characteristic com- 
pared with open loop gain response for 7 jinj second 



equalisation 
kisses 






head lasses 



3dB down 
points 



lOdHi ^kH7 

frequency 



Fig. 5.26. Overall frequency response from tape 
replay head and amplifier 



?!1 


do 
































IS 




































































s 




































-1 


































































in 


































11 


































-20 


i 1 


















4 















- 50 v 500 l-ik '„ 

frequency (Hz) 

Fig. 5.27. R.I. A. A. microgroove replay charac- 
teristic . < : 'V 




TR3 



-»v 



WWl 0-0W(jF <fj 

1 — s/W 

tookfi 




5-9 kfl. 



Fig. 5.24. Various tone correction characteristics 
are obtained with switched feedback paths. Position 
I for microphone, 2 for tape head replay, 3 for 
magnetic pick-up 




Fig. 5.28. Using an npn, pnp pair with fixed feed- 
back v\ ',*. " /> ■'<:« 



426 



while Rl enables this feedback voltage to be applied in 
series with the input, Fig. 5.21. 

This applied feedback increases the input impedance 
and decreases the output impedance. Rl should be 
kept low (less than 1 kilohrn) since this applies local 
feedback to the first stage. The amount of output fed 
back = B = RJiRi + M z ). Then gain with feedback 

n = —= ^ ~*~ ^ a = 1 + — ' 
B Ri R\ 

provided 1 + (RjRi) is much less than A in the usual 
way for negative feedback formulae. 

If the gain with feedback is such that RjR r is much 
greater than unity, then G = RJR t . 
Input impedance is given by 

this is shunted by the bias resistors at TR1 base. 
Output impedance is given by 

Pi -Pt 

— R 2 

■ Z °~h 

for a low source impedance i? s . 

A typical circuit of this type is shown in Fig. 5.22, 
which has a frequency response as shown in Fig. 5.23. 

Without feedback the input impedance Z x —■ 5 kil- 
ohms. Output impedance Z a = 6-8 kilohms. Mid- 
band gain is 52dB and bandwidth 14kHz. 

With feedback the gain is 38dB, which is what one 
might expect since the open loop gain is 52dB = 400 
times, while the closed loop gain 



G' = 



400 



^400 
' 100 



= 400 = 80 times = 38dB. 
5 



Ideal closed loop gain =100 times = 40dB 

Amount of feedback = 52 — 38 = 14dB 

Input Impedance Z x «= 8-2 kilohms 

Output Impedance Z = 200 ohms 

Maximum output is I50mV r.m.s. into Ik £2, and 

250mV r.m.s. for open circuit output. 

Noise referred to input = 5/iV r.m.s. for a 600 ohm 
source. Bandwidth is 66kHz, reducing to 20kHz with the 
820pF capacitor in circuit. The response is 3dB down 
when the impedance of the capacitor is equal to 
10 kilohms, in this case 19-4kHz. 

The feedback must be operative until a frequency 
lower than the low frequency 3dB down point of the 
amplifier, otherwise we could obtain a peak in the 
closed loop response. This is deliberately done for 
tape equalisation, where a rising If. response is required. 
This feedback arrangement is widely used in pre- 
amplifiers since, by switching the feedback network, a 
wide variety of frequency selective characteristics can be 
obtained. 

At the moment, the load is fed directly from the 
collector of TR2, which reduces the open loop gain. 
Feeding the load via an emitter follower increases 
the open loop gain to 65dB. For a tape head or 
magnetic pick-up input we require a high input 
impedance, but the high input impedance given by the 
negative feedback is masked by the shunting effect of 
the resistors biasing TR1. 



Bootstrapping these resistors enables us to take full 
advantage of the high input impedance provided by 
negative feedback. The modified amplifier suitable 
for use with switched feedback is now as shown in 
Fig. 5.24. 

Microphone Amplifier 

As previously shown this will have a gain of about 
40dB and a bandwidth of 20kHz. Input impedance is 
greater than 100 kilohms over the audio band. 

Tape Amplifier 

This has a gain of about 61 times (30dB) at 1kHz 
and an input impedance of 100 kilohms over most of the 
audio band, but the input impedance will drop at the 
low frequency end where it runs out of loop gain. 

The ideal response for 1\ in/second (70/is time 
constant) is shown in Fig. 5.25. Below 150Hz the 
amount of negative feedback is less than 12dB, so the 
equalisation is not going to be exact. This, coupled 
with the drop in input impedance would give an overall 
response out of the tape head, similar to that shown in 
Fig. 5.26 

Magnetic pick-up 

Here the mid-band gain is about 35dB, with R.I.A.A. 
equalisation. The input impedance is about 47 
kilohms, which is recommended for most magnetic 
pick-ups, this falls to 30 kilohms at 20Hz, which is 
acceptable. The equalisation is within i2dB of the 
required characteristic between 20Hz and 20kHz. 

The straight line approximation of the theoretical 
curve is given in Fig. 5.27, which is referenced to OdB at 
1kHz. The 100 kilohm impedance has been increased 
from the theoretical value (about 47 kilohms) to allow 
for the finite open loop gain at low frequencies (65dB). 

Summary 

Inputs at 1kHz for an output of 250mV 

Microphone. 2-5mV lOOkH 

Pick-up. 4-5mV 47k H 

Tape. 4-0mV lOOkO (7iin/sec and 70//s) 
Maximum output: 250mV into IkH 

For a simple amplifier of fixed feedback, it can be 
advantageous to use an npn, pup pair, as in Fig. 5.28. In 
this case 

Maximum output = 250mV r.m.s. 
Frequency response -±3dB 20Hz — 20kHz 
Gain 10 times = 20dB 
Input Impedance = 20k O 
Output Impedance =1500 

Next month: High input, low output impedance 
amplifiers and active filters 



For Future Reference 



An index for volume three (January 1967 
• to December 1967) is now available price 
Is 6d inclusive of postage. 

Orders for copies of the Index only should be 
addressed to the Post Sales Department, George 
Newnes Ltd., Tower House, Southampton 
Street, London, W.C.2. 



427 



Official 01 for 
Calibration Lab. 



The overworked National Physical 
Laboratory expects to be relieved 
of some time-consuming routine tasks 
following BCS (British Calibration 
Service) approval of the Ferranti 
Calibration Laboratory. 

"Outsiders" can now obtain help in 
a wide range of measurements covering 
frequency, d.c. resistance, inductance, 
capacitance, a.c. and d.c. voltage, 
current, and power. 

The calibration laboratory started at 
Ferranti's Moston works in 1940 and 
was transferred to its present site at 
Wythenshawe, Lanes., in 1954 to 
provide a service to the company's 
factories engaged in design and pro- 
duction of guided weapons. 

It was later made available to all 
Ferranti factories in the Manchester 
area, and in 1963 was extended to other 
manufacturers and organisations 
engaged on government contracts by 
obtaining EID part III test house 
approval, which covers a variety of 
electrical and physical measurements. 

The service was extended to all 
industries when the new BCS granted 
approval for d.c. and low frequency 
measurements. 



Type from Tape 



A Lancashire printing company, the 
Tinling Printing Group, has 
ordered an Elliott-Automation com- 
puter typesetting system for its Prescot 
works. 

The computer will automatically 
justify text (punched on special key- 
boards) and will produce complete 
pages in the form of punched paper 
tape. It also makes a record on 
magnetic tape for storage in case 
reprints are required. 

The completed paper tape is fed to a 
Photon typesetting machine which 
produces a positive of each page for 
making litho printing plates. 

Editing the book, and author's cor- 
rections, will also be easier and quicker 
because the computer adjusts the page 
make-up automatically to allow for 
alterations to the text during the proof- 
reading stage. 

(below) the magnetic 
and paper tape units 




Phosphor coated screen 




Picture Display 



Glass substrate 



ator Silicon 

Oxide thickened 
Bottom electrode Qlor,a 8<ta "- 
Aluminium 



The point-source electron gun 
(above) can be matrixed to 
produce a detailed display 




What could be the beginning 
of a semiconductor version 
of a television tube was demon- 
strated at the Physics Exhibition 
by STL Research, the prin- 
ciple used relies on the electron 
tunnelling effect, already to be 
found in tunnel diodes. 

The significant difference, 
though, is that electrons, after 
excitation in aluminium, are 
channelled through silicon oxide 
to a gold electrode. 

Free electrons are then re- 
leased into a vacuum to strike 
the phosphorescent coating on 
the display screen. The matrix 
(or raster) on the screen is 
made up from a series of tiny 
dots, each dot being related to 
its own semiconductor "gun". 

Current experiments by STL 
have shown that good alpha- 
numeric displays using 10 sq mm 
dots of activity are quite feasible 
and, in fact, could be developed 
on a commercial scale more 
economically than conventional 
methods. 

The size of the dot can be 
made very much smaller (about 
0-002in) to make up a fine 
screen matrix with a large 
regular pattern of dots. Repro- 
duction by photo-optic and 
electronic systems of live or 
photographic pictures becomes 
a possibility. The major hurdle 
to be jumped here, of course, 
is the vastly increased numbers of 
lead-out wires, but sequential 
display of each "dot" would 
reduce this number to practical 
proportions. 





[FOJJTT 




D.BOLLEN 



T'he PEAC basic equipment has now been dealt with 
and this month we commence a detailed description of 
the chief ancillary unit. Subsequent articles will cover 
the remaining two ancillary units. 

Perhaps it should be repeated at this stage that the 
three ancillary units are purely optional add-on items. 
The additional facilities they each provide, are indicated 
in the PEAC Specification (January 1968, page 38). 

PEAC UNIT "B" 

UNIT "B" reinforces the facilities of UNIT "A", but 
does not introduce new computing circuit elements. 
A master potentiometer and a suitably scaled readout 
meter improve the accuracy and ease of handling of 
UNIT "A", while the integrator mode switching circuit 
opens up further possibilities in the solution of Calculus 
problems. 

UNIT "B" FRONT PANEL 

It may not be necessary to use hardboard for the 
front panel if a thick grade of plastic laminate is used, 
since the wooden surround in the box front gives plenty 
of support. 

Prepare a 17£in x 8£in white laminate panel and 
establish hole centres with a sharp spike, from the 
drawings Fig. 6.1 and Fig. 6.2. Next, drill only the 
holes for all sockets, S7, S8, the meter mounting studs, 
and cut out a hole for the meter body with a fretsaw. 

Beginning with the master potentiometer dial, draw a 
300 degree arc of radius 2ftin with a pencil compass 
(refer to Fig. 6.2). Divide the arc into 3-degree divi- 
sions with protractor and pencil. The accuracy of the 
master potentiometer will benefit from careful pre- 
paration of the dial. Draw in the dial arc and divisions 
with Indian ink. 

Rub-on transfers are suitable for the dials of VR18 
and VR19, and will save time, but make sure that the 
transfer gives main divisions spaced at 30-degree 
intervals, for a 1-10 calibration. 

When dials are complete, drill holes to take the 



spindles of VR18-VR20, S9 and S10. Draw in all ink 
lines, add transfer numerals, and varnish. 
BOX CONSTRUCTION 

Commence building the UNIT "B" box by cutting 
out two side panels from hardboard; they are shown 
in Fig 6.3. Fix iin square softwood lengths A, B, C, 
and D to the inside of the side panels. Join the side 
panels together by means of horizontal lengths E, and 
F, using countersunk woodscrews and glue. Square 
up with the assembly placed on a flat surface. 

Cover the box framework with hardboard top, 
bottom, and front strip panels, and, when firm, reduce 
overlapping edges with a rasp and sandpaper. Finish 
off the box with a layer of white plastic laminate, and 
paint exposed hardboard edges to match the UNIT 
"B" box. 

MASTER POTENTIOMETER AND NULL 
METER 

A d.c. voltmeter connected to the slider of a comput- 
ing potentiometer will impose a small load, and when 
the voltmeter is removed the measured coefficient will 
increase slightly, to the extent of about 1-J- per cent in 
the case of a 10V 20,000 ohms/volt meter, and a 10 
kilohm potentiometer set with its slider near mid-track. 
One way of avoiding the error is to leave the voltmeter 
connected to the potentiometer after a coefficient 
reading has been taken, but this is seldom convenient. 

Ideally, the instrument used to measure coefficients 
or computer voltages should impose no load at all, 
and this condition can be satisfied fairly easily by 
employing an accurately calibrated master 
potentiometer. 

In Fig 6.4, a permanent load is placed on the co- 
efficient potentiometer CP by the computing resistor 
Rin f thus causing a significant dial setting error. To 
find the true coefficient of CP, both potentiometers are 
supplied with a reference voltage of + 10V, so that 
potentiometer coefficients of 0-1 will be multiplied 
by 10 to conform to a 0-10 dial calibration. When 

429 



COMPONENTS . . . 



UNIT "B" FRONT PANEL 

NOTE: All front panel controls ore numbered 
consecutively, following on from UNIT "A", but internal 
sub-assemblies have individual component numbering. 

Potentiometers 

VRI 8 I OQkQ carbon linear 

VRI9 lOOkft carbon linear 

VR20 25kft wirewound, 3in, 25W 
instrument potentiometer. (G. W, Smith 
& Co. (Radio) Ltd.. 3 Lisle Street, 
London, W.C.2) 

Switches 

57 Miniature push button, push to make, 

one pole 

58 Toggle, single poie changeover 

59 4 poie, 3 way rotary 
SIO 2 pole, 6 way rotary 

Sockets 

5 red, 3 black, 5 blue, 4 yellow, 4 white, and 
2 green 

Knobs 

One Buigin K403, 2fin knob with 3in skirt. 
Three Radiospares type PK l|in knobs with 
pointers 

Meter 

Ml "Sew" MR85P, 
resistance 1,000 ft 

Miscellaneous 

Plastic laminate (thick) for front panel, I off, 
I7£in x 8 fin. Rub-on dial transfers and 
letters, black (Radiospares) 

UNIT "B" MASTER POTENTIOMETER 
Resistors 

Rl 200ft R3 47Q R5 820ft 

R2 820ft R4 47ft R6 200ft 

All 5%, ^W carbon film or metal oxide 

Pre-set potentiometers 

VRI— VR4 1 00ft wirewound (4 off) 
panel mounting type 

Miscellaneous 

16 s.w.g. aluminium sheet 6in x 4in. Tag strip with 
three tags. 

UNIT "B" READOUT METER 



IOO-0-IQO^A, internal 




BUCK WHITE RED YELLOW BLUE GREEN 

Fig. 6.1. UNIT "B" front panel, integrator switching section 



Resistors 

Rl 82kft 10% 
R2 22kft 10% 



R3 7-5kft 5% 
R4 l-2kft 10% 



All |W, carbon 
composition 



Pre-set potentiometers 

VRI 22kft All miniature horizontal 

VR2 lOkft mounting skeleton con- 

VR3 2-2kft struction 

VR4 Ikft 

Meter protection diodes 

DI, D2 OC7I or similar "inverted" germanium 
transistor (2 off) 

Miscellaneous 

S.R.B.P. panel 2*in A 2in, 



UNIT "B" 


INTEGRATOR MODE SWITCH 


Resistors 




Rl lOkft 


R4 4-7kft R7 27kft 


R2 lOkft 


R5 27kft R8 4-7kQ 


R3 Ikft 


R6 Ikft R9 lOkft 



RIO lOkft RI2 3'3kft RI4 Ikft 
Rll tkft RI3 lOkft RIS 560kft 

All 10%, ^W carbon composition 

Pre-set Potentiometers 

VRI lOkft 

VR2 5kft Both vertical mounting 

Capacitors 

CI 1 ,000fiF elec. 15V 
C2 I ^.F polyester 250V d.c. C6 
C3 1-4/if polyester 250V d.c. C7 
C4 I4^F elec. 25V C8 

C5 0- i ^.F polyester 250V d.c. C9 



I /u.F polyester 250V d.c. 
I '4/xF polyester 2S0V d.c. 
14^F elec. 25V working. 
0-068/*F polyester 250V d.c. 



(The values of C3, C4, C7, and C8 are approximate — see text) 

Transistors 

TRI-TR6 ACY28orACI26. 
Diodes 

DI.D2 OA95 (2 off) 

D3-D14 IB30(Radiospares)(l2off) 

Reed Coils 

RLA. RLB Miniature triple 12V Osmor type MTI2V (2 off) 

Reed Switches 

RLAI— RLA3/Hamlin MRG2, 20-40AT (R.T.S. Ltd., 

RLB I— RLB3 \P.O, Box I I, Gloucester St. Cambridge) (6 off.) 

Miscellaneous 

S.R.B.P. panels: I off 6±in X 2£in; I off 3in x 2in. 

Small turret tags. 



430 




Fig. 6.2, UNIT "B" front panel, readout meter and master potentiometer 




WOOD (all Vg'xVg) 

® 2 OFF sVg" 
(D 2 OFF b% 
(C) 2 OFF A" 
® 2 OFF 8V4" 
© 2 OFF 16%* 
© 2 OFF 17 3 // 



2 0FFt2VBX7 1 / 2 (SIDES) 
1 OFF 18"X 6" (TOP) 
1 OFF 18"X10V 2 " (BOTTOM) 
1 OFF 18"X2V 4 " (FRONT STRIP) 



Fig. 63 UNIT "B" box 

constructional details 



431 



+10V 



CP 

COEFFICIENT 
POTENTIOMETER . 



AT NULL £ A =£ Z AND K IS THE 

TRUE COEFFICIENT OF CP 



NULL 
METER 




e z k 




+10V o+tv 
O-IOV O-IV 



MP 

MASTER 
POTENTIOMETER 



X 

METER PROTECTION 
DIODES 



VIRTUAL 
EARTH ,j,„ 



A> 

OP-AMP 



fig. 6.4. Master potentiometer circuit for measuring 
coefficients 



Fig. 6,5 (below). Circuit diagram of readout meter and 
master potentiometer 



the voltage at the slider of CP is identical to the slider 
voltage of MP, no current flows through the null 
meter, and the true coefficient of CP can be read straight 
off the dial of MP. 

Since no current flows at null point, no load is 
imposed, and the input resistance of the measuring 
circuit is virtually infinite. Meter protection diodes 
are included to preserve good meter sensitivity without 
allowing damaging currents to flow through the meter 
when the circuit is off balance. 

READOUT METER AND MASTER 
POTENTIOMETER CIRCUITS 

One meter movement serves for null indication and 
voltage measurement. Considering first the readout 
meter circuit Fig 6.5a, miniature p re-set resistors 
VR1-VR4 will permit calibration of each meter range 
to an external voltage standard, and also help to 
eliminate discrepancies between ranges. 

The way in which meter protection diodes Dl and 
D2 are wired may be unfamiliar to the reader, so some 
explanation is called for. If a transistor is operated 
"inverted", that is with collector-emitter polarities 
reversed, it will exhibit a very low "on" resistance 
when the base is near emitter potential. With base 
connected straight to emitter, the transistor therefore 
becomes a diode with lower than normal forward 
resistance, and yet will still offer a high resistance 



VOLTS 
INPUT 

Q 

SK1 



VR122UQ 




VR20 
SK2 SK3 SM SK5 



R1 82hfl 

Wv-VvV 
ma 

~1 R2 22kfl 



VS2 10kQ 



~~ 1 R3 MkQ 



VR5 2-2 ku 



UNIT "B" SOCKET 
IDENTIFICATION 

The following abbreviations 
will be used in program- 
ming instructions for 
PEAC. 

RM Readout Meter 
MP Master Potentiometer 
IS Integrator Switch 



~~1 R41-Eka 

m-VvV 




SK9 

-JOV 



+12-5V 



VR4 1M1 



READOUT METER 



MASTER POTENTIOMETER 

m 



EARTH 



-12- 5 V 



432 






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Signature . 



(If under 21 signature required of parent or guardian) 



NAME 

BLOCK LETTEHS 

FULL POSTAL 
ADDRESS 



433 



TRANSISTOR 
STEREO 8 + 8 




A really first -dnfcs Hi-Fi Stereo Amplifier Kit. Uses 1-f transistors giving 
8 watta push-pull output per chancel. (Iti \V mono). Integrated prc-nmp 
with Base, Treble and Volume controls. Suitable for use with Ceramic or 
Crystal cartridges. Output nt-tige for any speakers from 3 to 15 fib hi*. 
Compact design, all parts supplied incl tilling drilled metal 
work, Ctr-Kit board, attractive front panel, JiTiobs* wire, 

(colder* nuts, bolte— no extras to buy* Simple step by step 
instructions enable any conHiructor to build an amplifier to 
be proud of. 
Brief Specification: rreq. response — 3 db 20-20,000 t,'s. 
Bass boost .appro £, to +12 db. Treble cut approx, to 
—16 db. Negative feedback IS lib over main amp. 
Power requirements 25 V at H 6 amp. 



PRICES 

Amplifier Kit 
Built and Tested 
Power Pack Kit 

Built and Tested 
Cabinet (as iJIuj.j 



£9.10.0 

£12.10.0 

£2.10.0 

£3.0.0 

£2.(0.0 



P. & P. 4, 6 
F. & P. 4 6 
P. & P, 4/- 

P. ttr.il- 

P. ft P. 6/6 



(Special offer— £14.10.0. l'ost Free it all above kits 
ordered at same time or can be supplied built and tested 
tor £18.0,0 Post Free). 

Circuit diagram, construction details and parts list (free 
with kit) 1/8 (S.A.E.) 



STEREO AMPLIFIER 
Incorporating 2 ECLS6e and 1 EZ80, heavy- duty, 
double wound mains transformer. Output A watts 
per channel. Full tone ajjdjydlimc controls. Absolutely 

complete. 

ONLT 




£5.9.6 



r. it r. s/- 
Suner De- 
luxe version 
with ECL86 
valves, aep. 
hast, treble and balance con- 
trols. Full feedback. 8 gns. 

p. & r. a-. 




HIGH OAIN 4 TRANSISTOR 
PRINTED CIRCUIT 
AMPLIFIER KIT 
Type TA1 

• Peak out- 
put in excess 
ol I| -watts. 

• AH stan- 
dard British 
components. 

• Built on 
printed circuit panel siv.c u x ain. 

• Generous size Driver awl Output Transformers. 

• Output transformer tapped fur it ohni and 13 ohm 
speakers, • Transistors (liET 114 or SI Milliard 
OQS1D and malghcd pair of OC8I o/p). • 9 volt 
operation. t) Everything supplied, wire, batters' elips. 
solder, etc. # Ctiinprc'iensive easy to follow Instructions 
and circuit diagram 2/6 (Free with Kit). Alt parts sold 
separate I y. SPECIAL PRICE 45;-, F. & P. :t/-. Also 
ready Ituilt and tested, 62/6. F, i: F. 3/-. 

FM AM TUNER BEAD 
Beautifully designed and pre- 
cision engineered by Dormer 
and tVadsworth Ltd. Sup- 
plied ready titled with twin 
-0005 tuning condenser lor 
Alt connection. Frealigned 
I'M sec t ion covers 86-1 02 Hc/s. 
I.F. output 10*7 Mc,'s. Com- 
plete with ECC85 (6L12) valve 
and (ull circuit diagram of 
tuner head. Only 27/8 each. P 
MATCHED PADS AM/FM I.F.'S. 

2nd I.l'. discriminator. (465 Kc,! 10-7 Mc/Sh Size 
lin. ltin. :2^in. H. Will match above tuner head. 
11/- pair. F, & P. 2/.. 

QORLER F.M. TUNER HEAD. H!j-100 Me/a 107 Mc/s. 
I.F.. 15/-. Plus 2/6 P. 4i P. (ECC85 valves, 8/6 extra.! 
S.T.C. SILICON AVALANCHE HALF-WAVE RECTI- 
FIERS. Type RAM. 508 AF. o amps. &60 F.I.V, lin. long 
X ila. dia. approx. List SO/-. OUR PRICE 8/6. P. Free. 
SPECIAL OFFER '. FLESSEY TYPE 29 TWIN TUNING 
GANG, 400 pf -f 146 pf. Fitted with trimmers and 5:1 
integral slow motion. Suitable fnr nominal 470 kc/s, l.F. 
Size approx. 2*x 1'X 1J"- ONLY 8/8. P. * P. 2/6. 
FEW ONLY 1 SIEMENS MINIATURE RELAYS. D.P.C.O. 
Gold plated contacts. Size approx. 11" X J* X 11*. 6v. 
at 30 mA. ONLY 15/-. P. £ F. 1/6. 
NEON A.C. MAINS INDICATOR. For pane! mounting, cut 
out eiie 11 X tX Jin. deep inc. terminal. White cose with 
lens giving brighter light. For mains 200/250v, 2/6 each, 
F. & P. 6d* (6 or more post free). 

VIBRATORS. Large selection of 2, 4, 6, 12. 24 and 
32 Volt. Son-sync. 8/8; Sync. 10/-. P. A P. 1/6 per 
vibrator. S.A.E. with all enquiries, 
PRINTED CIRCUIT BOARD BY T.C.C. for Milliard 
3 valve tape amplifier SPECIAL OFFER 7/8, P. * P. 1/-. 




, & p. Jb>, Order quickly! 
Comprising 1st F.Y. and 





3-VALVE AUDIO AMPLIFIER MODEL HA34 

Designed for Hi-Fi reproduc- 
tion of records. A.C. Mains 
operation. Ready built on 
plated heavy gauge metal 
chassis, size 7 Jin, w. :: 4ln. 
d. :-: 4 lin. h. Incorporates 
ECC83, EL84, EZ80 valves. 
Heavy duty, double wound 
mains transformer and output 
transformer matched for 
9 ohm speaker, separate liass, Treble and volume controls. 
Negative feedback line. Output 4} watts. Front panel 
can be detached and leads extended tor remote mounting 
of controls. Complete with knobs, valves, etc., wired anil 
tested for only M.S. 0. P. Jl 1". H. -. 
HSL " FOUR " AMPLIFIER KIT. similar in appearance 
to HA 34 above but employs entirely different and mjt- 
vaiieed circuitry. Complete sci nf part s , etc , 79/6. F.&P. 0/- 
10,14 WATT HI-FI 
AMPLIFIER KIT 
A stylishly linished 
ruonaural amplifier 
with an output of 
14 watts from 2 
KLS4s in push-pull. 
Super reproduction 
of both music anil 
speech, with neg- 
ligible hum. Sep- 
arate inputs for 
tnlke and iiram 
allow records and 
announcements to 
follow each other. Fully whrnuded taBtfasil wound output 
transformer to match .l-.lafl speaker and 2 Independent 
volume controls, and separate bass :md treble controls are 
provided giving good Kit and cut. Valve line-up 2 EL84s, 
ECC83. El'BH. and EZMIJ rectifier. Simple instruction 
luMiklet 2 6. (Free with parts.) All parti sold separately. 
ONLY £7.B.B, P. £ P. 8/6. Also available ready built 
ami tested complete with std. input sockets, £9.6.0. 

1'. g P. gW. 

MAINS TRANSFORMER. Foe transistor power supplies. 
Prl. 200/240 v. Sec. 9-0-0 at fiOO mA. 11/-. P. & P. 2'6. 
Pri, 20O/24OV. See. 12-0-12 at 1 amp. 14/6. P. & P. 2/6. 
MAINS TRANSFORMER. For tcansistor power supplies. 
Tapped prS 200-250 v. Sec. 40-0-40 at 1 amp (with 
electrostatic screen) and 6'3v. at -5 amp for dial lamps etc. 
Drop thro 1 mounting, fclack size I2in. :' 3Jin. y. 'M\\\. 
27/6. P. & P. 4/6. 

MATCHED PAIR OF 2: WATT TRANSISTOR DRIVER 
AND OUTPUT TRANSFORMERS, Stack size II .' li .' 
i in. Output trans, tapped for 'A ohm and 15 obm out- 
put. 10/- pair plus 2/- P. k P. 

PARMEK0 7-10 watt OUTPUT TRANSFORMERS to 
match pair of ECL o2'e In push-pull. See. tapped 3-ffi. 
7 5 and 15 ohm. Stack elie 2l"X 1"X 2" approx. ONLY 
1U/-. P. & V. 31: 

7-10 mtt OUTPUT TRANSFORMERS to match p;Ur of 
ECL 86"s in push-pull to 3 ohm output. ONLY 11/-. 
P. & P. 2/6, 

10-12 watt OUTPUT TRANSFORMERS. Size 2Jiji. ■-. 2ln. 
Clamp fitting. For two EL84's in push-pull. State 3 or 

ta ohm imp.'dan::?. lg'6. 1'. .v 1'. ^- : ^^^ 

ACQS HIGH IMPEDANCE CRYSTAL STICK MIKES. 

Listed at 48/-. Our price, 21,'-, r. ft P. 1/6. 

ACQS CRYSTAL MIXES. High imp, desk or hand (1st. 

High sensitivity, 18/8. P. -J- P. ~ 

1/6. 

SPECIAL OFFER ! MOVING 
COIL MIKE, Fitted on/off 
switch for remote control . High 
quality. High or Low impe- 
dance. (State imp. re*id.) 
BARGAIN PRICE 30/-. 
P. 4 P. 2/6. 




HUGE PURCHASE: E.M.I. 4-Speed Player, 
Heavy 8 fin, metal turntable. Low- flutter 
performance 200/250r. shaded motor <90v. 
lap). Complete with latest type light- 
weight pick-up arm and mono cartridge ■ 
with Up styli for LP/78. LIMITED 
NUMBER. ONLY 83/-. P. & P. 6/6. 



4-SPEED RECORD PLAYER BARGAINS 
Mains models. All brand new in maker's packing. 
E.M.I, MODEL 999 Single player with unit mounted pick- 
up arm and mono cart. £5.5,0. 

B.S.R. GU7 Single Player with mono Cart £4.18,8 

B.S.R. UA25 Changer with mono Cart £6.7.6 

All pirn Carriage and Picking 6/8. 
LATEST GARRARD MODELS ALL types available 1000, 
S PU5, 3000 , A T60. etc JSend S . A . E . lor latest Bargain Prices ! 

BRAND NEW CARTRIDGE BARGAINS ! 
LATEST B.S.R. X1H MONO COMPATIBLE CARTRIDGE 
With turnover sapphire styli suitable for playing EF, LP 
and Stereo records with mono equipment. ONLY 22/9. 
P. ft P.l/8. 

S ON TONE 9TAHC Compatible Stereo Cartridge with 
diamond stylus 50/- or with sapphire stylus 40/-. 
P. & T. 1/6 each. 

QUALITY RECORD FLAYER AMPLIFIER 
A I op -quality record player amplifier employing heavy 
duty double wound mains transformer, ECC83, EL84, 
EKS0 valves, separate Dass, p Treble and Volume 
controls. Complete with output* transformer matched 
for 3 ohm speaker. Size 7ln. w. :; aln. d. X 6ln. b. 
Ready built and tested. PRICE 75/-. F, * P. G,'-. 
ALSO AVAILABLE mounted on board with output 
transformer and speaker ready to fit into cabinet below. 
PRICE 97/6. 1*. A P. 7/6. 

DE LUXE QUALITY PORTABLE R/P CABINET 
L'ncut motor board size 141in. v 12in. clearance 2ln. 
below, 5Iin. above. Will take above amplifier and any 
B.S.R. or GARRARD Autochanger or Single Player Unit 
(except AT60 and SF25). Xi?.B 18in. .: 15ln. St Sin. 
PRICE £3.9.8. V. fs P. 9/6. 

VYNAIR AND REXINE SPEAKER AND CABINET 
FABRICS app, 64ln. wide. Usually 85/- yd., our price 
18/8 per yit. length. P. A P. 2/6. (min. lyd,). S.A.E. for 
sa mples. ^ 

BRAND NEW 3 OHM LOUDSPEAKER8 
6ln..l4/-; 6Jlo.. 18/8; Sin., 27/-: 7ln. x 4ln. 18/8: lOin, 
' win., 87/6. E.M.I. Sin. ;< Sin. with hi gli flux magnet 21'-. 
E.M.I. 13iin. : 8in. with high fltiJt ceramic magnet, 42;-. 
(15 ohm. 45/-). P. & P. ain. 2/-. 6 tin. M 8ln. 2/6, lOin. & 
lain. 3/6 per speaker. 

BRAND NEW. 12lu. 15w. H/D Speakers, 3 or 15 ohm. 
Current production by well-known British maker, OfTered 
below list price at 89/8. P. <It P. a,'-. Cultar models: 
25w. £5.5.0; 35w, £8.8.0. 

E.M.I. 31 in. HEAVY DUTY TWEETERS. Powerful 
ceramic magnet. Available in 3, 8 or 15 ohms. 15/-. 
P. & P. 2/6. 

12in. "RA" TWIN CONE LOUDSPEAKER. 10 watts 
peak output. 3 or 15 ohm. 35/-. P. &. P. 3/6, 

35 OHM SPEAKERS 
3Jin. 12; 8; 7 X 4ln. 81/-. P. * P. 2/- per speaker. 



HARVERSON SURPLUS CO. LTD. 

170 HIGH ST., MERT0N, S.W.I 9 01-540 3985 

Open all day Saturday Early closing Wed., I p.m. 

A few minutes from South Wimbledon Tube Stotion. (Pleose write cleor/y} 

OVERSEAS P. ft P. CHARGED EXTRA. S.A.E. with all. enquiries 



The most accurate 
pocket size 

CALCULATOR 

in the world 



The 66 inch OTIS KING scales give 
you extra accuracy. Write today 
for free booklet, or send 82/6 for 
this invaluable spiral slide rule 
on approval with money back 
guarantee if not satisfied. 

CARBIC LTD. (Dept. pei7) 

54 Dimdonald Road, London, S.W.19 



?£* *'*- 




BOOKLET ON 

REQUEST 



All items previously ad- 
vertised available, also tee 
items advertised in Prac- 
tical Wireless. Huge Hi- 
Fi and Components stocks 
at all branches. 



EGHNWAL 
TRADING 



•k LONDON (MUS 2639) 
10 Tottenham Court Road 

* PORTSMOUTH 

(Tef. 22034) 
350-351 Fratton Road 
-A- SOUTHAMPTON 

(Tel. 25851) 
71 East Street 

* BRIGHTON (Tel. 2397S) 
6 Queen's Road 

oil mo if order Brighton 



FANTASTICALLY POPULAR 



TAPE 



We otter yon lully tensllised polyester, mylsr 
and P.V.C. tipei ol Identical quality hi-fi, wide 
range recording characteristic! as top grade 
tares. Quality control manufacture. They 
tie truly worth a lew more coppers than 
acetate, sub-standard, jointed or cheap imports 
TRT ONE AND PROVE IT YOURSELF. 



Standard Play 


Look Play 




3iit. 150ft. 


m 


Sin, 229ft. 


2/9 


4in. 300ft. 


4/8 


4in. 460ft. 


5/8 


Sin. 609ft. 


7/8 


Gin. 900ft. 


10/8 


5 Jin. Lioofi. 


10;6 


S|iu. 1.2001 1. 


13F 


7in. 1,200ft. 


18/8 


7in. 1 ,800ft. 


18 6 


Double Play 




Triple Flay 




3m. 300ft, 


|£" 


4in. 900ft. 


1SS7- 


4in. 600ft. 


ti- 


Sin. 1,800ft. 


86/- 


Sin. l,200fl. 


lth 


5]in.2,400lt. 


34/- 


5 Jin. 1, 800ft. 


18/6 


7in. 3,600ft. 


44/- 


7in. 2,400tt. 


87/- 


Quadruple Play 






3in 600ft. 


8/8 


PottnQtt I/- reef. 








Post Free less 5"i 


on thi 


ree rests. 





Quantity and Trade en tallies invited. 

NOTE. Large tape jfocJti nf all tranche*. 



434 



reverse characteristic. The arrangement eliminates the 
need for a meter series resistor while still giving ade- 
quate protection. 

In Fig. 6.5b, VR20 is a 3in instrument potentiometer 
of good linearity. The voltage divider network, 
composed of R1-R6 and VR1-VR4, taps off four 
standard voltages from the computer power supply, 
so that the master potentiometer will measure inputs 
of to + IV, to - IV, to + 10V, and to - 10V 
on its 0-10 scale. The accuracy of the master potentio- 
meter, bearing in mind the 14in scale length, approaches 
that of a laboratory voltmeter. 

FRONT PANEL AND MASTER 
POTENTIOMETER ASSEMBLY 

Mount all sockets, potentiometers VR18-VR20, 
switches S7-S10, and meter, on the UNIT "B" front 
panel. Make up an aluminium bracket from the 
measurements given in Fig. 6.6, and glue it to the front 
panel, along with the small tag strip, in the position 
shown in Fig. 6.7, A hot soldering iron applied to the 
aluminium bracket will solidify the epoxy resin glue in a 
matter of minutes, sufficient to hold the bracket in 
place until the joint sets hard. 

Rest the front panel inside-out on the UNIT "B" 
box front, to protect panel markings during assembly. 
Mount pre-set voltage divider potentiometers VR1-VR4 
to the aluminium bracket, and then proceed with the 




.r&^jJT^ 




Fig. 6'6. Mounting bracket for preset potentiometer* 



MASTER POTENTIOMETER 



READOUT METER 




GLUE BRACKET AND TAG STRIP 
TO FRONT PANEL WITH 
EPOXY RESIN 



TO POWER PACK 



Fig, 6,5, Rear view of UNIT "B" front panel, showing 
master potentiometer and readout meter wiring 



435 



r 



i 



DRILL j DIA.TO 

TAKE METER 
TERMINAL SCREWS 




MATERIAL: 
S.R.B.R. BOARD 



Z^ 



& 



S° V° %° N 







-2^- 



Fig. 6.8. Meter resistor panel, underside view 

wiring of master potentiometer components, using 
20 s.w.g. tinned copper wire and sleeving. 

READOUT METER ASSEMBLY 

Make up the meter resistor panel shown in Figs 6.7 
and 6.8, and attach to the meter terminals. Solder Dl 
and D2 to MP/SK1 and RM/SK2, then complete S10 
and resistor panel wiring. 

As centre-zero voltmeters with 10-0-10 and 3-0-3 
scale calibrations are not readily available, a scale will 
have to be made. Perhaps the most satisfactory way 
of fabricating a new and really accurate meter scale is to 
draw it two to four times full size, photograph it, and 
then have the resulting negative enlarged back to the 
original size on glossy photographic paper. The 
enlarging can be done commercially if the oversize 
drawing carries a thick black line to represent a length 
of lin on the finished scale, just outside the scale 
perimeter. 




When taking the photograph, ensure that the camera 
lens is in line with the centre of the scale card, and that 
the film plane is parallel to the surface of the oversize 
drawing, to prevent optical distortion. 

Another tip, use white Formica for the drawing, 
as then mistakes in ink can be erased without leaving 
unsightly grey areas. 

To remove the existing scale from the meter, prise 
off the transparent meter front, and carefully remove 
the scale card by undoing the two holding screws. 
Measurements can then be taken for preparing the 
oversize drawing. 

To fit the new scale, cut out the photographic repro- 
duction and paste it over the old scale, with edges and 
mounting holes of both scales properly registered. 

SETTING UP MASTER POTENTIOMETER 
AND READOUT METER 

With red, green, and blue p.v.c. covered wires, 
connect the master potentiometer tag strip (Fig 6.7) 
to the solder tags on the power pack output terminals. 
Also, temporarily link the rear of MP/SK2 to the green 
earth wire. Rotate VR20 spindle fully clockwise 
and patch MP/SK2 to SK3, MP/SK5 to SK6, MP/SK1 
to SK4, and link RM/SK2 to VS1 /SKI . Switch on the 
computer and S6, and adjust VS1 for an exact + 10V. 
Now obtain a null on the readout meter by setting VR1 
on the voltage divider bracket, from the back of 
UNIT "B" box. 

Repeat for VR2 with an input of + IV by transferring 
the patching lead plug from MP/SK6 to SK7, and again 
for VR3, SK8, with an input of -IV, and VR4, SK9, 
with an input of — 10V. 

After that, while still nulling with a — 10V input, 
rotate VR20 spindle slightly clockwise, until the meter 
pointer just begins to. move away from zero. Place 
the large knob on VR20 spindle, with the transparent 
plastic cursor aligned with the "10" division, and tighten 
the grub screw. Set VR20 cursor to the "5" division 
and check for null with an input of — 5V. It may be 
necessary to slightly re-position VR20 knob on the 
spindle, and trim VR1-VR4 again to minimise errors. 

Calibration of the readout meter is straightforward. 
Apply a selection of known voltages to RM/SK1 and 



SIN6LE SHOT 



CLOSED 



OPEN 



CLOSES 



0PEM 



Fig. 6.9. Diode clamp circuit, 
showing principle of operation 



436 



Nearly 1,700 Circuits and Diagrams plus full repair data for 

800 POPULAR MODELS 




1968 RIGHT BACK TO 1965 

RADIO & TV SERVICING 

Big time-saving repair library 
to step up your earnings 

Now off the Printing Presses — a great new edition of RADIO 
A TV SERVICING, to save your time, to boost your earning- 
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previous editions sold. Now you can 
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once stocks are sold and there's 
absolutely no obligation to buy under 
this free trial offer. 



FULL DATA & CIRCUITS 
FOR REPAIR OF 

• TELEVISIONS including 

COLOUR TV 

• RADIOS, RADIOGRAMS 

• CAR RADIOS 

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• TAPE RECORDERS 



...J- ■ . CI3 6 .^v 



Printed pane! diagrams 



Pry s^«rt g r> 



mH 



ax Wr K£ f* m 
WO MO vtH" "~ B2T. 



A 



Component layout diagrams 




SERVICING DATA FOR ALL THESE MAKES 

Aiwa, Alba, Baird (including colour TV), Beogram, Beolit, Bush, Carousel, 
Cossor, Dansette, Decca, Defiant, Dynaport, Dynatron, Eddystone, Ekco, 
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TV), Grundig, H.M.V., Kolster-Brandes, Hitachi, Invlcta, McMlchael, Mar- 
coniphone, Masteradio, Motorola, Murphy, National, Newmatlc, Pam, Perdlo, 
Peto-Scott, Philips (including colour TV), Portadyne, Pye, Radiomobile, 
R.G.O., Regentone, Roberts' Radio, Sanyo, Sharp, Smith's Radiomobile, Sobeli 
(including colour TV}, S.T.C., Sony, Standard, Stella, Stereosound. Teletron, 
Thorn, Trans Arena, Ultra, Van Der Molen, World Radio. 

am m » A I ATFCT OVER 1,500 PAGES, PACKED WITH CIRCUITS, 

P L If S «P l r,L.,r»,rr COMPONENT LAYOUT DIAGRAMS, PRINTED 

** ** DEVELOP MEN TS panel diagrams, tables and waveform 

IN RADIO AND TELEVISION graphs. 

Including— integrated Tuners, Stereo Multi- 
plex Broadcasting — The Zenith-G.E. System. 
Receiver, Decoder and adjustments, Aerial, 
etc. Colour TV Receivers, Colour TV Test 
Card F, Servicing Transistor Equipment, 
Chemical Aids to Servicing, Batteries and 
RechargeableCells,Sound-on-Sync, Double 
Line Sync, Silicon Transistors, etc. 



Handsomely bound in rich maroon and gold. 

| To: Buckingham Pran Ltd., 18/19 Warren Street, London 
, Please send Radio and TV Servicing — 3 volumes without 
I obligation to buy if you accept my application. I will return 
the books in 8 days or post : 

I Tick (/) □ Full cash price of £12, or 

a here □ 15/- dep. and 16 monthly payments of 15/-. 



.w.il 

I 



Drive-cord diagrams 



LL, I, A 



I 7 2, I Zi3 






Block diagrams 



Sent to your home post paid on 

7 DAYS 
FREE TRIM 

Absolutely no obligation to buy 



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I with coupon. Elsewhere overseas add 10/- 
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TDc address ib left It 
■My W properly | | 

Rented , 

uriFurnistitilLi 
FjirnisbedicGorcQ' 

1 Tempurary _ 
MM 



& P. KY J JO/U 



437 



■ovoro con. multimeter tk as, 

0-I,0OO». A.C./D.C. ob mi to 100k. etc., 

SUPEH10K MOVING COIL MDXTIMETEB. 
0-feBOOT. D.C. 20.000 ohmi per »o». 0-l,000r, A.C, 
Obmi to meg. SO Microanipt. (Full list Meters S.A.E 



49/6 
99/6 



NEW MULLARD TRANSISTORS 

OC71 6.'-: OCT2 6/-: OC81D 8/-; OC81 6/-: AF115 BM 
AF114 8/8; OCM 8/-; OC46 6/-; OC171 8/-; OC170 8,-; 
AF117 8,'-. OC28 12.0; AD140 IS/-: Ocas 16/- Holderi 1 - 
EEPANC0 TRANSISTOR TRANSFORMERS 

TT4S. Fash Pall Drlrer B;1CT. bV- 

TT48,Ptuh Pall OatpolCT 8:1. 8/- 

TTIB. Interstage, eto, 4.5:1 B/- 

TT62. Ootoat 3 obmi 20:1 8/- 

TEAMSISTOR MAINS ELIMINATORS. FAMOUS MAKE 
FULLY SMOOTHED. PULL WAVE CIRCUIT. AQlt 
8 VOLT. MOmA Sue 6xljx 2io. tT/O 

DITTO TRANSFORMER ONLY. Size 21 X U X litn....l0/8 

WEYRAD PJ0 — TRANSISTOR COILS 



KA2W 6 to. Ferrite Aerial 

witb ctr aerial coil 12 8 

CMC F6CV1AC S/4 

I.F.P50/2CC 470 kc/i ... 5/7 
3ld I.F. P50/3CC 8/- 



Snue Corel Bd. 

Driver Trans. LFDT4 S/B 

Frl nted Circuit. PC A 1 . .9/8 

J.B. TaDinit Qbiik 10/3 

Weyrad Booklet 2/- 



tW- each 

250-0-250 80 mA. 0.3 T. 3.5 a. 8.3 », 1 I, or 5 y. 2 a. 80/- 
350-O-350 SO mA. 8.3 v. 3.5 a. 0.3 v. 1 a. or 5 v. 2 a. 35 - 
300-0-300 v. ISO mA.. 0.3 v. 4 a. C.T.; 8.3 y. 2 a. 45/- 

MINIATTJRE 200 y. 20 mA., 8.3 t. 1 a 12/8 

MIDGET 220 y. 45 mA., 8.3 v. 2 a 17/8 

HEATER TRANS. 8.3 T. 1!- a.. 8/8: 8.3 v. 4 a 12/6 

Ditto tapped sec. 1.4 v., 2, 3. 4, 5. 8.3 v. 1> amp. . . 12/8 
GENERAL PURPOSE LOW VOLTAGE. Output! 3. 4, 5. 

8, S. 0. 10. 12. 15, 13, 24 and 30 T. at 2 a 30/- 

1 amp., 8, 8, 10, 12, 16, 18, 20, 24, 30. 38, 40, 48, 80, 35'- 
AUTO TRANSFORMERS 0-115-230 y. Input/Output, 
80w. 18/6; 160W.30/-; BOOw. 02/6: lOOOw. 175,'-. 



CRYSTAL MIKE INSERTS 

L| v. lin. 6 '8; ACOS 1: < lie. 8,6. BM3. 1" din. 9,6 

MOVING COIL MIRE with Remote Control Switch 18/6 

ALL PURPOSE HEADPHONES 

H.R. HEADPHONES 2000 obmi - 19/6 

H.R. HEADPHONES 2000 ohms Super Quality ...... 35/- 

LOW RESISTANCE HEADPHONES 3-5 ohma 35/- 



Teleicopic Chrome Aeriali 61a. exteudi to 23in. 5/- 



Volume Controls 

LONG SPINDLES. MIDGET 
SIZE 5 K. ohms to 2 Mes. 
LOG or LIN. L/S 3/-. D.P. 5 I- 
STEREO L 'S 10, 8. D. P. 14 6, 
5K. S.P. Edge Type 5'-. 



80 ohm Coax 8d. yd. 

SEMI-AIR SPACED 
40yd. 20/-; 60yd. 30/-. 

FRINGE LOW LOSS I IJL. 
Ideal 625 lines I /«*«• 



5 wait 
10 watt 

15 watt 



r w- 

< 2/- 

L 21- 



COAXIAL PLUG 1/3. PANEL SOCKETS 1,3. LINE SOCK- 
ETS 2/-. OUTLET BOXES, SURFACE OH FLUSH 4/6. 
BALANCED TWIN FEEDERS 1/- yd., SO or 300 oh mi 
CAR AERIAL PLUGS 1/6. SOCKETS 1/3; LIKE SOCKETS 2, ■ 

SELCOL 
TRANSISTOR 
AMPLIFIER 
ONE WATT 
POWER OUTPUT 
Portable Cabinet siie 12 X 4 
X 8tn. fltted 7 X 4in, Speaker, 
Volume Control, Standard 
lack Socket. Uaei PP9 Bat- 
tery, Will increaie volume aud performs nee 
of Transistor Radios, Record Playert, Tape Recorder!, etc. 
Ideal lor Guitar practice. OUR TQ If. POST 

Worth Double! PRICE '"/<* 5/S 

RETURN OF POST DESPATCH 




RESISTORS. Preferred values, 10 obmi to 10 meg. 
t w.. I w.. 1 w., S0% 3d.: li w. 8d.: 2 w. 1/-; i w, 10% 8d 
HIGH STABILITY, i w. 1% 10 obmi to 10 meg.. 2/- 
Ditto 5°i>. Prelerred values 10 obms to 22 meg., 9d. 

-i 0.5 to 8.2 ohm 3 w. 

K WIRE-WOUND RESISTORS 

J 10 obmi to 6, 800 ohms 

1PK, 15K, 20K, 25K. S8K, 10 W, 3/- 
SPEAKER FRET Tygan various colours, 52in. wide. Irom 
10/- It.; 26in. wide Irom 5/- It. SAMPLES S.A.E. 
EXPANDED METAL Gold or Silver 12 X IS in. 6 -. 
VER0B0ARD 0.15 MATRIX 
2; ■; Sin. 3/8d. 2: X 3JIn. 5/2d. 32 x 3Jiu. 3/8d. 
EDGE* CONNECTORS 18 way 5;-; 24 way 7/6. 
FINS 36 per packet 3 4d. FACE CUTTERS 7/6. 
S.R.B.P, Board 15 MATRIX 2;in. wide 6d. per lip; 8iin. 
wide Bd. per lin: Sin. wide 1/- per lin. {up to 17in,; 
BLANK ALUMINIUM CHASSIS. 18 i.w.g. 2Jiu. aides. 
7x4in., 6.0; flx 71b., 6/0: 11 x Sin, 6/6; llx71n. 7/6; 
13 --Sid, 9. e : 14 x llin. 12/6; 15xl4in., 15/-. 
ALUMINIUM PANELS 18 f.w.g. 12 < 12in. 6/6; 14 x Sin. 
5/ 8; 12 x Sin. 4/6: 10x7tn. 3/8; 8* Sin, 8/6; 6x4in. 1/6. 

THE INSTANT 

BULK TAPE 

ERASER AND 

RECORDING HEAD 
DEMAGNETISE!? 



ALL EAGLE PRODU CTS 

EAGLE AM TUNER. Medium Wave. 70 A 
Traniiitor Superbet. Ferrite aerial, etc. t wjv 

EAGLE DE LUXE TAPE SPLICER Cuts, trims, 17/X 
Joins tor editing and repairs. With 3 blades, I / / W 

EAGLE 4j CHANNEL TRANSISTOR MIXER. Add 
musical highlights and sound effect! to recording!. Will 
mix Microphone, record i, tape and tuner with C Q I A 

■eparate controls into siegl eoulput. . J ' / ** 

EAGLE DYNAMIC MICROPHONE, Impe- £L If. A 
dance 600 obm/50K. 70-12,000 cps. Universal i-W.IU.W 



mounting, stick, hand or itand. 



Proleisiona I quality, 

EAGLE FM TUNER 88-103 Mc s Six Transistor. Ready 
built. Printed Circuit. Calibrated elide dial /Q I ft ft 
tuning. Size 6' X V X 81'. fco » ■ v ' v 



EAGLE 3 WATT AMPLIFIER. 4 Translator 
Push-Full Ready built, with volume control w '/ 

40-PAGE EAGLE CATALOGUE 51- Poit Free 



69/6 



* RADIO BOOKS -* (Postage 3d.) 

High Fidelity Speaker. Enclosures aud Plans... 5/- 

Transistor Superhet Commercial Receivers 7/6 

Milliard Audio Amplifier Manual 8/6 

Radio Valve Guide, Books 1, 2. 3, or 5 each 5/- 

Fractica! Radio Imide Out 4/6 

Tr amis tor Audio Amplifier Manual Book 1, 3/8; Book 2, 6/- 

Sbortwave Tr a osistor Receive ti , 5/- 

Traniiitor Commnnication Sets 6/- 

Interuational Radio Stations Lilt 2/6 

Modern Traniiitor Circuits lor Beginner! 77S 

Sub-Miniature Transistor Receivers , 6/- 

Wireless World Radio Valve Data 9/8 

At a glance valve equivalents , 91- 

Valves, Transistors, Diodes equivalents manual . 10 '6 



WIRE-WOUND 3-WATT 
POTS. T.V, Type. Values 
10 obmi to 30 K„ 3/3, 
Carbon 30 K. to 2 meg., 3/-. 



WIRE-WOUND 4-WATT 
STANDARD SIZE POTS. 
LONG SPINDLE VALUES 
50 OHMS to 100 K., 7/6. 



200/250 V. A.C. 
Leaflet S.A.E. 



Minimum Post and Packing charge 2/6, 




VALVE HOLDERS. MOULDED Sd; CERAMIC 1 - EACH. 
SCREENING CANS 1:.; VALVE BASE PLUGS 2 3. 

5ANGAMO 1 inch SCALE METERS 4S> ii. 

Varioui calibration! and movement!. 100 Microamp; 
1 Mllliamp 50-0-50 Mkroampi, etc., S.A.E. lor list, 

BRAND NEW QUALITY 
EXTENSION LOUDSPEAKER 

Black plastic cabinet, 20 It. lead and 
adaptor!. For any radio. Intercom, tape 
recorder, etc. 3 to 15 ohm. POST 7f| I 
SUe: ?r x Si" x 3" 2/6 ■>«/" 

C.O.D. 51- extra. Full List (/-. CALLERS WELCOME 




RADIO COMPONENT SPECIALISTS 337 WHITEH0RSE ROAD, WEST CROYDON 

Written guarantee with every purchase, (Export: Send remittance and extra postage, no C.O.D.) buses 133,68 pass dewcS.fi. Stn. Selhurst. Ttl. 01 -684-1 66B 



NEW RANGE BBC 2 AERIALS 

AH U.H.F. aerials now fitted with tilting bracket 
and 4 element grid te Sectors. 

IjOft Mounting: Arrays, 7 element, 37/C 
11 element, 45/-. 14 element. 58/6. IS element, 
so. -. Wall Mounting- with Cranked Arm, 
7 element, 60/-. 11 element, ST/-. 14 element, 
T5/>. 18 element. 82/6. Mast Mounting; with 
21n, clamp. 7 element, 42/8; 11 element, 55/-; 
14 element, 62/-; 18 element, 70/-. Cnlnmey 
Mounting Arrays, Complete. 7 element, 
72/6; 11 element, 80/-; 14 element, 87/6; 18 element, 
W/-. Complete assembly Instructions wltn every 
unit. JLow JLoss Cable, 1/6 yd, TJ.H.F. Pre- 
amps from 75/-. State clearly channel numbet 
requited on all orders. 



BBC 




ITV AERIALS 

BBC (Band 1). Telescopic 
loft, 25/-. External S/D, 30/-. 
"H", £2.15.0. 

ITV (Band 3). 3 element toft 
array, 30/-, 5 element, «/-. 
7 element, 50/-. Wall mountine, 
3 element, 47/6. 5 element, 53/6, 
Combined BBC/ITV. Loft 
1+3, «/-; 1+5, 50/-; 1+7. 
60/-; Wall mountimj 1 +3, 57/6: 
1 +5, 67/6; Chimney 1 +3, 67/6; 
1+5,75/-, 

VHF transistor pre-amps. 
75/-. 

COMBLVEO BBCt— ITV— BBCS AERIALS 

1+3+9. 70/. 1+5+9, IN, 1+5 + 14, It/-. 
1+7+14, 1MI-. Loft mounting only. Special 
leaflet available. 

F.M. (Band X). Loft S/D, IS/-, "H", 32/6, 3 
element, 55/-. External units available. Co-ax. 
cable, 8d. yd. Coax, plugs, 1/4. Outlet boxes, 5/-. 
Dip lexer Crossover Boxes, 13/6. C.W.O. or CO.D. 
P.&P. 5/-. Send 6d. stamps for Illustrated lists. 

CALLERS WELCOME 

OPEN ALL DAY SATURDAY 

K.V.A. ELECTRONICS (Dipt, p.e.) 

27 Central Parade, Ntw Addington 
Surrey— CKO-OJB 
LODGE HILL 2266 




MATERIALS FOR THE RADIO 

CONTROL DEVICES IN THIS 

ISSUE AVAILABLE FROM 

TELERADI0 

Specialists in 
Radio Control Systems 

Send S.A.E, for breakdown price lists 

of the components required, 

quoting P.E./RC/68 

TELERADI0 ELECTRONICS 

325-7 FORE STREET 
EDMONTON, LONDON, N.9 

01-807 3719 



NEW 1968 Edition 

RADIO AMATEUR 
HANDROOK 



45/- 



by A.R.R.L Postage 4/- 



WORLD RADIO T.V. HANDBOOK, 

1968 ed. «/-. Postage I/-. 

MULLARD DATA BOOK, 1968. 3/6. 

Postage 6d. 

RADIO AND AUDIO SERVICING 
HANDBOOK, by G. J. King. 30/.. 

Postage I /6. 

MATHEMATICS FOR RADIO AND 
ELECTRONICS TECHNICIANS, by 

Ing. F. Bergcold. 50/-. Postage 1/6. 

RCA TRANSISTOR MANUAL. 20/-. 
Postage I/-. 

Inter GEC. S.C.R. MANUAL 4th ed. 

25/-. Postage 2/-. 

COLOUR TELEVISION PAL 
SYSTEM, by G. N. Patchett. 40/-. 
Postage l/-, 

TRANSISTOR POCKET BOOK by 

R. G. Hibberd. 25/-. Postage I/-. 



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of British and American Technical Books 

19-21 PRAED STREET 

LONDON, W.2 

Phone; PADdington 41 85 
Closed Saturday I p.m. 



438 



oLJbed 




!! If 



3 157" I | Iw I Jot" I 1ms I 



D100CS: DJ-D14 1650 GOLD SOHDCD 



MtEN 



5K3 



SK9 SK7 SK4 SKI 

Fig. 6 JO. The complete circuit diagram of the integrator switch 



adjust VR1-VR4 on the resistor panel for optimum 
accuracy on each range. 

INTEGRATOR MODE SWITCHING 

The simplest type of integrator switch employs a 
mechanical relay with several sets of contacts, driven 
by an astable multivibrator, and this system is used for 
small demonstration and educational analogue compu- 
ters. The relay is arranged to "gate" the inputs of 
several amplifiers simultaneously. 

The PEAC integrator switch goes a stage further, with 
reed relays for a "clean" switching action at high speeds, 
full initial condition facilities, and a circuit based on 
two independently timed monostable multivibrators. 

Referring back to the basic integrator switch shown 
in Fig 1.2c, two changeover switches SI and S2 are 
opened and closed in a pre-determined sequence, 
governed by an external timing circuit. It is important 
to ensure that integrating amplifier input resistors are 
not left floating when they are disconnected from the 
virtual earth summing junction, as this could seriously 
disturb input and other computer voltages, hence the 
presence of SI and S2 earthed contacts. 

DIODE CLAMPS 

To eliminate the need for expensive reed switches 
with changeover contacts, diode clamps can be used 
instead of an earthed contact, see the alternative 



amplifier circuit of Fig 6.9. The diodes do not inter- 
fere with the normal working of the integrator, but 
will nevertheless hold resistor junctions close enough 
to earth to prevent load variations when SI and S2 
are open, and this modification more than halves the 
cost of switching components. 

In the block diagram of Fig 6.9, the 1st monostable— 
controlled by VR18 — determines the period of closure 
of SI. When SI opens after a timed interval, a pulse 
is delivered to the input of the 2nd monostable, thus 
closing S2. S2 will remain closed for an interval 
controlled solely by VR19. 

For "single shot" operation, a trigger pulse applied 
to the 1st monostable input, when S8 is switched to 
"hold", will initiate the closure of SI (reset) and bring 
the integrating amplifier to its initial condition. 

As soon as SI opens, S2 closes (compute) and 
connects input resistors to the summing junction. At 
the end of the compute period, SI and S2 are both 
open (hold), the monostables are quiescent, and the 
amplifier output voltage is held steady by the action of 
capacitor Ct. The next computer run is started by 
another trigger pulse applied to the 1st monostable input. 

Repetitive operation is achieved by passing the 
output pulse from the 2nd monostable back to the input 
of the 1st monostable, when S8 is switched to "repeat". 
SI and S2 are then made to open and close alternately, 
and the "hold" facility is deleted. 

439 



The method of inserting an inital condition voltage 
is as follows. When SI is closed the reset resistor R T is 
connected between the amplifier output and summing 
junction, and can therefore be regarded as a feedback 
resistor in parallel with Ct. 

As long as SI remains closed, Ri c will be acting as an 
input resistor, so that 



E Q = — £h 



E± 

Ric 



and E = — Eic when R r = Ri C . Ric and R T are dis- 
connected from the amplifier summing junction when 
SI opens, but Ct will "remember" the initial condition 
voltage and hold the amplifier output steady prior to the 
application of compute voltages when S2 closes: 

INTEGRATOR SWITCH CIRCUIT 

The complete circuit of the integrator switch is shown 
in Fig 6.10, The 1st monostable consists of TR2 and 
TR3, with RLA actuated by emitter follower TR1, 
VR18 continuously covers two ranges given by C3 
(10-1 00ms), and C4 (0-1-ls). Components associated 
with the 1st monostable input are C2, Rl, and Dl. 

The 2nd monostable is almost identical to the 1st. 
TR4 drives RLB, CI and C8 offer the same timing range 
coverage as C3 and C4, and input components are C6, 
R8, R9, and D2. However, more care is taken to 
establish the correct values for 2nd monostable timing 
capacitors CI and C8, and VR2 allows precise calibra- 
tion of the "fast end" of the VR19 timing scale, so that 
compute intervals can be determined by a reasonably 
accurate dial setting. 

VR1 establishes the working point of both mono- 
stables, to achieve reliable operation at all dial settings. 
S7 is a push button on the front panel for starting a 
"single shot'.' computer run. Full control of an oscillo- 
scope trace, from UNIT "B" front panel, can be 
realised by suitable connection to the integrator switch 
circuit. With S8 switched to "hold", the mode 
sequence can be triggered repetitively, with a variable 
hold interval, by the oscilloscope timebase output or 
by a separate oscillator. Consistant syncronisation of 
the trace, with continuous or single-sweep timebases, 
is made possible by linking IS/SK10 to an appropriate 
oscilloscope input 

A SEPARATE SUPPLY 

The load capacity of the existing stabilised power 
supply can be improved by wiring the collectors of 
TR1 and TR4 (shown dotted in Fig. 6.10) to a separate 
— 12V unregulated supply, which can be housed inside 
the UNIT "B" box, and in this event CI could be 
omitted from the Fig. 6.10 circuit, as it merely serves 
to prevent current pulses from flowing in the negative 
stabilised supply line during relay switching. 

RLA and RLB consist of two triple-switch coils, 
catering for the needs of three integrating amplifiers. 
A duplicate relay panel could be added later, by 
wiring relay coils in parallel, to increase the switching 
capacity to six amplifiers. 

CORRECTION 

In Fig. 5.7, the captions for the first and second oscillo- 
graphs (top row, left and centre) should be transposed. 

Next month: Assembly and setting up of the 
Integrator Switch; practical examples in the use 
of this section. Introduction of UNIT "C" 
Function Generator. 



next month ! 



Build this 
DRILL 
SPEED 
CONTROLLER 





An invaluable accessory giving 
controlled drill speed at constant power. 
Easy to build from full instructions in 
next month's issue. This small, com- 
pact unit incorporates a simple thyristor 
circuit, providing smooth variation of 
drill speed by finger-tip control, 
ALSO 

MULTI-CHANNEL RADIO CONTROLLED 
MODEL BOAT 

The second part of this feature contains details 
of the electromechanical drive system and the 
power supply 

WAA-WAA 

A modern effects unit for electronic guitars 



PRACTICAL 

ELECTRONICS 



JULY ISSUE ON SALE FRIDAY JUNE 14 

Order your copy now! 



440 



Budding 
technician? 

In just 15 months, the Army 
could set you up for life! 

Think it over. In just 15 months, you could have 
completed an Army course in electronics. You'd have 
trained with the most modern equipment and now 
you'd be handling it as though it was second nature. 
You'd be earning nearly £14 a week — with all your food 
and accommodation thrown in. And you'd be 
looking forward — in about eight months time — 
to promotion to corporal and the pay rise that goes 
with it. It's a great life all right. 
And if you're between 17-23 it's wide open to you. 
Get the facts by filling in the coupon or calling 
at your local Army Careers Information Office 
(address from any Post Office). 




r£g*— For-aM 
the facts send 
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please send me the latest free army leaflet, 



NAME 

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I TOWN 

COUNTY DATE OF BIRTH 




£ 




BREADBOARDING 

SINGLE DeCs, One S-DeC with Control Panel. Jig and 
Accessories for solderiess connections to controls, etc.. with 
booklet ' Projects on S-DeC ' giving construction details for 
a variety of interesting circuits 29/6 + 6d. P. & P. 

4-DeC KIT. Four S-DeCs with two Control Panels, Jigs 
and Accessories and the booklet ' Projects on S-DeC ' all 
contained in a strong, attractive plastic case. Ideal for the 
keen enthusiast and professional user £5.17.6 -f- 2/6d. P. & P. 



^&;M 



■ 





Four-stage binary counter using the 4-DeC Kit 

* S-O.C AVAILABLE FROM ELECTRO Ml QUE DEALER5 
AND LEADING SUPPLIERS 



In ease of difficulty in o&lai nmg from a re toiler post this form ! 

Please send rne S-DeCs kits and 4-DeC 

kits for which I enclose P.O./Cheque/Money Order 
value C / ../- 

NAME 



ADDRESS 



To: S.D.C. PRODUCTS (Electronics) LTD, 

THC CORN EXCHANGE, CHELMSFORD, ESSEX 



I 

I 
I 
I 

I 

I 

I 

m 

I 
I 
I 

441 



ORGAN BUILDERS: S.P.K. Hi]. Planar Transistors. All Tested, 1/8 each or (5.0.0 

per 100. 

TRANSISTOR BARGAIN SALE : HEW STOCK AT UNBEATABLE PRICES I 

OC44, OC40, OC81D now only 1/6 each! *8.0.0 per 100 

OC71, OC73 equivalent 1.'- each! £3.0.0 per 100 

ASY22 Switching Transistors 2 6 each: £10.0.0 per 100 

2N763 X.P.X. Silicon Planar. SOOruAV. 250Mc;b. High speed switching . . E/8 each: 

B8Y28X,F.X. Silicon Planar. Epitaxial, 300rnW, 300MC/S .. .. 8/6 eachl 

BBY60 X.F.N. Silicon Planar, Epitaxial, BOOmW. 10OMc/s .. 8/6 eachl 

AFZ12 P.X.F. Germanium Alloy Din", low noise V.H.F. Hinvlitter . . 8/6 each: 

Complete acta of transistors tor radio: 

2G344.V'2G345A/2G345B/2G371A/2G37KA,2C37HA + diode .. .. 10/'- only: 

Hi IT 120, 2 watts. Heat sink included 8/6 each: 

Transistor Driver Transformer!) ., .. .. ., -. .- 8/6 each! 

Transistor Output Transformed (suitable lot our kits above) . . 8/6 each! 

QC28 .' .. ■- 6/- each! 

BYZ13, 6 amp rectifiers. SPECIAL REDUCED PRICE! ONLY 2/6 each; 84/- doz.; 
£7.10.0 per 100: £60.0.0 per 1,000. 

Light sensitivity translators similar to OCP71 8/- each: 

UNMARKED, UNTESTED TRANSLATORS TO CLEAR . . . . 7/6 lor 50 1 

Silicon diodes. Make excellent detectors. Also suitable for keying electronic organs, 
l/-each; 20 for 10/-. 

BY100 type rectinem. SPECIAL REDUCED PRICE: ONLY 8/6 each; 84/- doz.; 
17.10.0 per 100; £50.0.0 per 1.000. 

ELECTROLYTIC CONDENSERS! FANTASTIC SELECTION ! 



0-20fiF 


3 volt 


6*tF 


1/lP 


GO volt 


SfiF 


lfiF 


. . 360 volt 


8jiF 


l-atiiF 


16 volt 


1(!l" 


3fiP 


3 volt 


8|iF 


3jiF 


9 volt 


8,uF 


2 ( iP 


70 volt 


8j*F 


2*iF 


. . ISO volt 


10(tF 


QuF 


. . 360 volt 


18/iF 


2-fl/iF 


16 volt 


20jiF 


2'fl/iF 
3/tl' 


26 volt 


20/jF 


3 volt 


SO^lF 


3fjF 


25 volt 


SOijF 


3-2yxF 


6-4 volt 


25fiF 


3-2mF 


64 volt 


SfiuF 


*i& 


4 volt 


2S(iF 


*>F 


12 volt 


25pF 


4uF 


26 volt 
64 volt 


30«F 
30fiF 


4*tF 


100 volt 


6mF 


6 volt 


40ixF 


BjaF 


26 vott 


40/xF 


All at 1/- 


each. Mixed P* 


ckets oi 



3 volt 

3 volt 

6 volt 

360 volt 

450 volt 

60 volt 

276 volt 

26 volt 

. . 160 volt 

3 volt 

volt 

9 volt 

16 volt 

6 volt 

12 volt 

16 volt 

26 volt 

6 volt 

10 volt 

3 volt 

6-4 volt 

I (out selection) 10/ 



oOfiF 

64nF 

64jiF 

100/jF 

lOOirF 

lOO^F 

150/tF 

2Q0(iF 

200j«F 

260,uF 

SSOfiF 

320/xF 

350jiF 

350j*F 

400^F 

400^F 

EOOj^F 

500uF 

640iiF 



9 volt 
2-0 volt 
9 volt 
3 volt 
6 volt 
9 volt 
32 volt 

3 volt 

4 volt 
2-8 voit 

9 volt 

2-6 volt 

9 volt 

10 volt 

2-5 volt 

15 volt 

4 volt 

6 volt 

2-6 volt 



PAPER CONDENSERS 

0'OOlfiF . . 600 volt ! 002(iF . 600 a.c. 

OOOlfiF . , 1000 volt ! 0-02ftF . . 380 volt 

00O2ptF . . 600 volt 0'1/lF . . 360 volt 

0-006yF . . 760 volt I 0-ljiF . . 750 volt 

All at 15/- per 100, 3/- per dozen. Mixed Bags of 100 (our select km) 10/-. 



0-25>F 
0-6uF 
0-5itF 



360 volt 
360 volt 
500 volt 



HULLARD POLYESTER CAPACITORS. ALL HALF PRICE 



0-0O22fiF 400 volts 
00018pF 400 volts 
0-0G16/iF 400 volts 
OOOlfiF 400 volts 
e-01nF 400 volta 
68pF Tubular pulse ceramic 



4d 0'18uF 160 volts 

4d 0-22fiF 160 volte 

4d 0-27^1' 160 volts 

4d OOSGfiF 126 volte 

W 1/xF 125 volts 
6d each 



7d 

7d 

3d 

M 

1/6 



VERY" SPECIAL VALUE: Silver Mica, Ceramic, Polystyrene Condensers. 
Well assorted. Mixed types and values, 10/- per 100. 

RESISTORS. Give-away offer I Mixed type* and values, t to i wo tt. 

6/6 per 100 or 55/- per 1,000. Individual values, Sd each". 

Also 1 to 3 watt close tolerance. Mixed values, 7/6 per 1O0; 55/- per 1,000 

WIRE-WOUND RESISTORS. 1 watt, 3 watt, 8 watt, Sd each, 7 wstt and 10 watt 

M tach or 20 mixed types 10/-. 



CONNECTING WTRE. TEW, P.V.C. INSULATED. 

10yd, 1/-; 100yd. 7/8: 500yd , 85/- (post 4/6) ; 1,000yd, 40/- (post 6/-). 

VALVES. BRAND-NEW AND BOXED. ROCK-BOTTOM PRICES: 



6/B 1 EYS6 
7/- ! EY87 



7/* 
7/4 
7/1 
8/6 
?A 
7/1 
9/5 
B/S 
6/9 



PABC80 

PC97 

PCC84 

PCC89 

PCF80 

PCF80 

PCL82 

PCL83 

PCL84 

PCLS5 



8/8 I I'CLSS 
6/9 PFL200 



7/1 
10/6 

7/4 
10/6 

8/S 
1CA ' 

8/5 
9/10 

8/5 

8/5 



PL36 
PL81 
PL83 
PL84 
PL500 
PY32 
FY81 
PY82 
PY800 



B/6 
11/8 
10/1 

8/5 

8/6 
6/6 
12/5 
B/- 
6/3 
4/8 
6/8 



DY87 

EABC80 - 

ECC82 

ECC83 ,. 

ECL80 

ECL86 

EF80 

EF86 

EF183 

BP184 

EY51 

A further 10% discount will be given on lots of 50 of any one type. 

RECORD PLAYER CARTRIDGES 

Acos GP67/29 Mono, 16/-; Acos GP91/35C Stereo compatible. 20/-; Acos (1F94/1 

Stereo, 86/-. All with needles. 

Transistorised Signal Injector Kit- — 10/-. 
Transistorised Signal Tracer Kit— 10/-. 

VEROBOARD. All sizes in stock. 

2iin x lin 0-16 matrix 

2,|Q x 3(in 015 matrix 

2Jin x 5Jin 015 matrix 

3(in X 3, in 0-15 matrix 

3fln x Sin 01a matrix 

17in x 2 jin 0-lfi matrix 

SPECIAL OFFER! 

Cotter and 6 Boards 2Jin x lin. B/8. Cutter onlv, 7/6. pin Insert Tool, 8/6. Terminal 

Pins. Packet of 36, 8/8. 

m aH OFFER! 

Few only Multimeters, 1,0000 per vott, 46/- 



1/1 


17in 


: 3] in 


t> Id matrix 


. . 14/8 


3/8 










3/11 


oin 


'. 2] in 


01 matrix 


.. 8/11 


3/11 


Sjin 


: 2 t ln 


0-1 matrix 


.. S/S 


6/6 


Sin 


: 3{tn 


ii- 1. matrix 


6/8 


u/- 


3] in 


. 3] in 


1 matrix 


.. 8/11 



20,0000 per volt, 80/-. 



Orders by post to: — 

G. F. MILWARD, 17 PEEL CLOSE, DRAYTON BASSET, Staffs. 

Please include suitable amount to cover postage. Stamped addressed envelope must 
be Included with any enquiries. 

For customers in the Blrmiogbam area goods may he obtained from Rock Exchanges. 
231 Alum Rock Road, Birmingham 8. (All POST orders to Drayton,) 
MIJfTMUM ORDER 10/- 



SH0RT WAVE ONE 
RECEIVER KIT 



VALVE 



39/6 + 2/6 P.P. 



PEAC ANALOGUE COMPUTER KIT III STOCK 



£26.0.0 + 15/- P.P. 



UNIT 'A' COMPLETE 

Punched aluminium panels and 

case for above £4.17.6 + 

CLUBMAN Mk. I KIT COMPLETE £6.17.6 + 

Without metal work £4.12.6 + 

CLUBMAN Mk. II KIT COMPLETE £10.17.6 + 

Without metal work £8.12.6 + 

EXPLORER KIT COMPLETE £4. 2.6 + 



5/- P.P. 
5/- P.P. 
2 6 P.P. 
5/- P.P. 
4/6 P.P. 
2/6 P.P. 



STABILIZED POWER SUPPLY KIT Q-20V. 500ma 
COMPLETE £4.17.6 -\- 5/- P.P. 

COMBINED AUDIO OSCILLATOR AND FREQUENCY 
METER £17 + 10/- P.P. 

PORTABLE TEST UNIT KIT 
FLUORESCENT CAMPING LIGHT IN STOCK 

S.A.E. FOR TRANSISTORS, SEMICONDUCTORS, FULL LIST 

700 TYPES 

3 SILICON RECTIFIERS, BY! 00 TYPE 10/- 

10 MIXED MARKED TESTED TRANSISTORS 10,- 

40 UNMARKED UNTESTED TRANSISTORS NEW 10/- 

1 LIQHT SENSITIVE CELL 0RP12 8/6 

25 MIXED UNMARKED TESTED TRANSISTORS 10/- 

2 TRANSISTOR C0MP. PAIR ADI6I/I62 16/'- 
P.P. 1/- 

OUR COMPONENTS CATALOGUE 5/- Post Paid with 10/- worth of 
discount vouchors. 

OLRUS ELECTRONICS LTD. 

748 HIGH ROAD, LEYTONSTONE 

(NEXT TO GREEN MAN) 

LONDON, E.11. Tel. 01-989 2751 

CALLERS WELCOME— CLOSED ALL DAY FRIDAY 



• CA 3020 (LINEAR I.C.) 

V Io lS-Leafl to -5 Cms / 



INEAR 

Lead to -5 Cute t 

AMPLIFIER 



WIDE-BAND 



COMPLETE WITH DATA SHEET 3a. - EACH 

AXUMINIOM DIECAST BOXES— Appros. dinieiiBion»: Type -\ 41 3] lin. 
ilcep at 7/8 eai]h. Type B 4J :; 3| X 2in. deep at 10/- ench. 

SUBMIJMATiJEE TAGBOAEDS— < I j In. wide), rt-way at 1/8. 3 8-way at i/- each. 
COAX. SOCKET ftortiM movnttng, Xylon Siunlatett. 1/8 each. 

COAX. PLUS— Belling Lee Typo 1,734, 1/4 each. 

BESISTOES— CARBON PH.M— I wait, 5°I, 10 nhtn to 10 -Megohm. 3£d cacti or 
3/3 dor.. 

CAEBOH PfiESET POTEHTIOKETEES— Vertical or Horizontal mounting. 
200 ohm to 2 Megohm. (Standard value?) at 1/4 each. 

KDiIATURE CARBON POTENTIOMETERS - ■ l in - ilia. iiu. deep; !in. dia. 
Hpinrtle. 5 Kohm to 2 Meirohm LO<:. and 5 Kohm to 1 Megohm. LIN. at 3.'- each 
or 2/0 each for 4 or more of the same value. (Standard values only.) 

CAPACITORS— CERAMIC TUBDLAB -(Standard Values) J'TpF- OOl^iP 
3d each. 

CAPACITORS— SILVEB MICA— 5pF SCOpF 1,'- each (Standani Values). 

CAPACITORS — TANTALUM BEAD—A range of 3<i miniature units, with 
values Irora 100fxF/3vw to 01fjF/33vw all values at 4/3 each. 

BEEHIVE TRIMMERS— -a -30pF) at 2 8 each. 

DIODES— OA70, OA71, OA7B, OAfll, OA85, OA01, OA200, OA202 at II- each. 

THASSISTOBS OC44, 6/8; OC43. tt/4; OC7I, 3/B; OU72, 5/4; OCS3. «/-; 
OC170, 7/8; BC107. 3/11: BC10S, 8/3; BCI09, 3 11; BCIOO. 6 -: OtslZ. 10,'-: 
AC127Z. 8,8; B8YSSA. 5'8; SKTS1S, 4/4; NKT2IH. 3/11; NKT228. 3/11: 
NKT871, 3/4; NKT274. 8/4; NKT075, 4/3; NKT773, 4/8; 2t;a02, */-; 2G371, 
B/10: 2N70B, 8/B; 2NB97, 6/-; 2N305S, 8/B; 2.N3638. 5/8; 2N3702. 8/9; 2N3703, 
4/-; 2N3704, 6/-; 2N3705. 4/8; 2X3706. 3/8; 2X3707, 4/8; 2N3708, 8'4; 2X3709. 
8/B; 2X3710, 3/8: 2X3711, 4/3: 2X381SKFKT). 14 '8; 2X3H20t FET). «}/-; 
2X2646(1?JT). 10/8; BR¥3BtSCS). 10/8: A WIDE RANCH-: OF OTH ER TYPES 
ARE IX STOCK. IXCLUDINO 2N2926 SERIES All groups at 8,3 each 
(or, 8/8 each In multiples of 5). 

Postage and packing is charged at I,- in the t (Minimum of 8/' per order), 

M. R. CLIFFORD & COMPANY (COMPONENTS DEPT,). 
209 A, MONUMENT ROAD, ED GB ASTON. BIRMINGHAM, 16. 
Turns: C.W.O. (or C.O.D.— over £3 only] Tel.: 021-454 8SU 



442 








BASSETT 



The "cymbals" circuit with the white noise generator, 
described last month, can be adapted to give a "whoosh" 
effect to the sound of drum beats. A microphone is 
placed in close proximity to the drums; the signal from the 
microphone is passed through the "whoosh" unit. The 
effect produced can be tuned or filtered to give different 
pitches for each drum beat. 

WHOOSH TRIGGER 

The unit described incorporates its own microphone 
amplifier to give sufficient drive to trigger the whoosh 
into action. Referring to the circuit in last month's 
cymbals effects article, the signal is fed into C7 from the 
heavily driven amplifier shown in Fig. i. 

This amplifier cannot be used as an ordinary audio 
amplifier or pre-ampHfier for normal listening purposes, 
as its output would be pulsed and highly distorted; how- 
ever, it is very suitable in this case for providing a pulse 
drive to the cymbals circuit. This latter circuit is triggered 
to pass white noise from the P.E. White Noise Generator. 

Refer to the block diagram on Fig. 2. The sound of 
the drum is picked up by the microphone, which is placed 
close to the drum skin. The signal passes to the high- 
output-swing amplifier via a volume-control VR2. 

The output pulses from the amplifier then operate the 
cymbal circuit, whose output can be heard as a "whoosh" 
by connecting to a power amplifier. A single-pole 
push/push switch may be connected from the junction of 
D2, D3 to chassis, in order to mute the unit when effects 
are not required. 

The cymbals filter circuit is altered to give a lower 
"whoosh" sound rather than a cymbal effect. This 




Fig. I. Circuit diagram of the microphone amplifier 



alteration consists merely of increasing the values of C5 
and CIO to GOS^F; CI and C8 become OOl^F, and 
RIO is decreased to I megohm. Different values may be 
tried, thus altering the effect to your own personal prefer- 
ence. It is necessary to adjust the volume controls (both 
the sensitivity control VR2 and the volume control on your 
audio amplifier) after changing the capacitors, as they have 
a considerable effect on the output amplitude of the unit. 

If VR2 is set too high, acoustic feedback can occur, 
resulting in a continuous "whoosh" effect from the loud- 
speakers. Therefore, VR2 is set a little lower, so that a 
tap on the drum is necessary before the "whoosh" effect 
is produced. Other sounds, for example, from an electric 
guitar or organ, should not be allowed to trigger the whoosh 
unit. Another measure, which may be necessary in order 
to avoid this continuous "whooshing" feedback is to 
position the loudspeakers well away from the drums. 

MAKING THE MODS 

To make this effects unit you will need the basic white 
noise generator and cymbals filter boards (see last month's 
article). Carry out the modifications to the cymbals 
filter board as detailed earlier; fit these two units into a 
chassis or other box 12in x 4in x 2jin, leaving space 
for the new microphone amplifiers and possibly the 18V 
power supply. 

The "manual pulse" push-button SI and resistor R7 
are not necessary and can be omitted if desired. The 
"pulse input" jack JK1 is not necessary either and can be 
transferred for use as the microphone input jack. 

A muting push-button is fitted to the chassis and 
connected in parallel with D2 on the filter board. 





HIGH -OUTPUT- 
SWING 
AMPLIFIER 



SZo 



zr. 






24 V 



MODIFIED 

CYMBAL 

GATE 

CIRCUIT 



L-o A 



OUTPUT 
SK2 



negative bias 
(if required) 

fig. 2. Block diagram showing the interconnection of 
panels with jacks and controls 

443 




COMPONENTS . . . 



To microphon«JM 4 Fixinq holds Vg dio 




Fig. 3. Printed circuit pattern 
(full size) for the microphone 
amplifier 



Fig. 4. Component layout 
on the printed circuit board 



MICROPHONE AMPLIFIER 

Resistors 

RI IMC" R3 22kQ R5 22kQ 
R2 ISOkfl R4 2-2kQ 
All 10% ±W carbon 

Potentiometer 

VR2 lOkQ log. carbon 

Capacitors 

CI I0 M F elect. 15V 
C2 I0 M F elect. 15V 
C3 100 M F elect. 10V 

Transistors and Diode 

TRI.TR2 ME4l03orC424 
Dl ISI30orDD0OG 

Miscellaneous 

Printed circuit board 2in x l£in 

Other components are as given in the Cymbals 
Effects Unit article last month except: 

Change C5 to OOS^F C7 to QOI^F 

C 1 to 005^F CB to 00 1 ^F 

RIO to I MO 

Delete SI and R7 

Add Single pole on/off switch in parallel 
with D2 (push on/push off) 



Next, the new panel incorporating components for 
amplifying the microphone signal is made up. The 
printed circuit pattern is shown full size in Fig, 3, while 
component layout is given in Fig. 4. Terminal points on 
the board can be either pins or direct connections to the 
copper through holes in the board. 

All printed circuit boards can be glued on to foam 
rubber or plastics pads in the box so that the copper does 
not touch the metallic chassis; plain s.r.b.p, boards can 
be used here to separate the printed circuit boards from the 
metal. 

TESTING THE EFFECTS UNIT 

Connect the unit to a power supply of 18 to 24 volts, also 
a negative bias supply for the cymbal circuit. The power 
source may consist of either batteries or a mains power 
unit with smoothed output (as shown in last month's 
article). Connect also a power amplifier with loud- 
speakers (a guitar amplifier or public-address amplifier is 
suitable). All variable controls should be set initially 
to a low level. Temporarily connect the junction of 
R8, C8 (cymbals filter) to the positive supply and switch 
on. 

By adjusting VR1 and the volume control of the audio 
amplifier, the sound of the white noise generator should 
come through in a filtered form; the controls should now 
be adjusted to give a fairly loud, continuous low-pitched 

444 



hissing effect. Remove the positive supply connection 
from the junction of R8, C8 S and this sound should die 
away. 

By adjusting VR2, you will find that sounds received 
by the microphone are transformed to give a whooshing 
effect from the loudspeaker. VR2 can be set so that 
only the loudest sounds have this effect, and if the micro- 
phone is mounted near to, and facing, the skin of a drum, 
only a tap on this drum will produce an output from the 
unit. 

USING THE UNIT 

The unit may be used with just one particular drum, 
which is the simplest arrangement. Alternatively, several 
different drums may be used, each with its own microphone. 
If a number of identical microphones are used, these may be 
simply connected in parallel using screened wire. Alterna- 
tively, an audio mixer unit may be used in place of VR2, to 
feed signals from a number of different sources to the 
input of the amplifier. The microphones used may be an 
inexpensive crystal type, or a moving-iron diaphragm 
unit. 

In order to obtain a different "whoosh" sound from each 
drum, you may wish to build a separate "whoosh unit" 
for each drum, and feed the output from each unit to the 
power amplifier by way of a mixer unit. <X* 



BUILD YOURSELF A QUALITY TRANSISTOR 
RADIO— FULL AFTER SALES SERVICE! 



THE MAGNIFICENT 

RQAMER 



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RADIO WITH A SUPER SPECIFICATION 

i 7 FULLY TUNABLE WAVE BANDS— MW1, MW2, LW, SW1, 
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i Extra Medium waveband pro- 
vides easier tuning of Radio 
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i Built in ferrite rod aerial for 
Medium and Long Waves. 

i 5 Section 22 in. chrome plated 
telescopic aerial for Short Waves 
— can be angled and rotated for 
peak S.W. listening. 

i Socket for Car Aerial. 

i Powerful push-pull output. 

1 7 transistors and two diodes 
including Philco Micro- A Hoy 
R.F. Transistors. 

i Famous make 7x4 in. P.M. 
speaker. 



• Air spaced ganged tuning con- 
denser. 

• Separate on/off switch, volume 
control, wave change switches 
and tuning control. 

• Attractive case with hand and 
shoulder straps. Size 9 x7 x4 in. 
approx. 

• First grade components. 

• Easy to follow instructions and 
diagrams make the Roamer 7 a 
pleasure to build with guaran- 
teed results. 



Total building costs 

£5.19.6 p * p 





Parts price list and 
easy build plans 3/ 
(FREE with parts) 



Total building costs 

42/6 -*/• 



MEDIUM WAVE, LONG WAVE 
AND TRAWLER BAND 
PORTABLE 

Attractive case with red speaker grille. Size 61 x 
4J x IJIn. Fully tunable. 7 stages — 6 transistors 
and 2 diodes — ferrite rod aerial, inning condenser, 
volume control, flue tone super dynamic 2] in. 
speaker, all first grade components. Easy build 
plane and parts price list 1/6 (FREE with parts!. 




Total building costs 

39/6 \% p - 



MEDIUM WAVE, LONG WAVE 
AND TRAWLER BAND PORTABLE 

At tractive black and go.d case* Size BJ K 3 J M 
3]tn, Fully tunable over both Medium and Long 
Waves with extended M«W. band tor easier tuning 
*>t Luxembourg, etc* All first grade component*! 
T stages — 5 transistors and 2 diodes — super- 
sensitive lerrite rod aerial, fine tone 2 Jin, moving 
coll speaker, etc, Easy build plans and parts 
price list, 1^6 (FWBE with parts). 




NEW MELODY MAKER SIX 

3 WAVEBAND PORTABLE 8 stages— 6 transistors and 2 diodes 

Covers Medium and Long Waves and EXTRA M.W. BAND FOR EASIER TUNING OF 

LUXEMBOURG, etc. Top quality 3in. Loudspeaker for quality output. Two RF 
stages for extra boost. High "Q" 6in. Ferrite Rod Aerial. Approx. 350 milliwatts push-pull out- 
put. Handsome pocket size case with gilt fittings. Size 6i >; 3i x liin. 



This amazing receiver 
may be built for only 



69/6 



P. &. P. 4/6 



Parts Price List and easy build plans 2/- 
(Free with parts). 



ROAMER SIX 



tiding costs 
P. & P. 

4/6 



SIX WAVEBAND PORTABLE 
WITH 3in. SPEAKER 

Attractive case with gilt fittings, size ?f X M x 
IJIn. World wide reception. Tunable on Medium 
and Long Waves, two Short "Waves, Trawler 
Band plus an extra M.W. band lor easier tuning 
of Luxembourg, etc. Sensitive Jerri te rod aerial 
and telescopic aerial for Short Waves. All 
top grade components, 6 stages — 1> transistors 
and 2 diodes including Philco Micro-Alloy K.F. 
Transistors, etc. {carrying strap 1/6 extra). Easy 
build plans and parts price list 2/~ (FREE with 
parts). 



A SUPER SEVEN 



THREE WAVEBAND PORTABLE 
WITH Jin. SPEAKER 



Total building costs 

69/6 '-V 



Attractive case size 7£ x 51 X 1) In. with gilt 
fittings. The ideal radio tor home, car or outdoors. 
Covers Medium and Long Waves and Trawler 
Band. Special circuit incorporating 3 R.F. stages, 
push-pull output, ferrite rod aerial, T transistors 
and 2 diodes, 3ln. speaker (will drive larger 
speaker) and all ttrit grade com po Bents. Price 
list 21- (FREE with parts). 



RADIO EXCHANGE Ltd 



Callart side entrance Stylo Shoe Shop. Open 9-5 p.m. Saturday 9-12.39 p.m. 



61a HIGH STREET, BEDFORD 
Telephone: Bedford 52367 



445 



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FULL CIRCUIT - INSTRUCTIONS - PARTS 

LIST TO BUILD YOUR OWN 

TELEPHONE ANSWERING / RECORD 

MACHINE - QUICK - AUTOMATIC 

TAKES 100's OF CALLS: 
CHEAP TO BUILD. SEND NOW 



'ir 



25/- 
2/6 



7' AMPEX TAPE SPOOLS, ONLY 

P. & P. 6d. 

KING'S TELE-SERVICE CO. 

105/107 DAWES ROAD, FULHAM, S.W.6 

FULHAM 1668-2998 




£7/5/0 



Solve your co mm uni ca- 
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4-Ststicn TiasMitor Intercom system (1 muter anil 
8 Bobs], in de-luic plastic cabinets (or desk or wall 
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Subs to Hitter, Ideally suitable for Busi nose, Sur- 
gery, Schools, Hospital. (Mice anil Home. Operates 
on one SV battery. On/oft switch. Volume control. 
Complete with 3 connecting wires each I'ltlfi. and 
other accessories, P. & P. 7/C. 
WIRELESS INTERCOM 
Ho btttwisi — no mitt*. Just plug in tin- Mctim (M 
Instant two-way, loud and clear communication. 
On/off switch and volume control. Price 18 (mi. 
P. fc P. 7/8 ertra 




Same as 4-StatlS'tl intercom for two-way instant 
communication. Ideal as Baby Alarm and Door 
Plione, Complete with GGtt. connecting wire. Battery 
218. P. A P. 3/6. 

BM_ 

59/6 

Why not boost 
business efn. 
cieoey with this incredible De-Ion Telephone Ampli- 
fier. Take down long telephone messages or converse 
without holding the handset. A useful office aid. On/ 
ott switch. Volume control. Battery 3/6 eitra. P. & 1". 
1IC. Pall price refunded If not satisfied in T days. 

WEST L01TOOJI DIRECT SUPPLIES <P/K6) 
189 KEISnOTOBT HIGH STREET. LONDON, W.S 




VALVES 



SAME DAY SERVICE 

NEW! TESTED! GUARANTEED! 



QBTQ !R0. 196- 1T4. 384, 3V4, DAF91. DF91, DK9I, DL92, DL94 
O C I O get i 4 j or 17/fl, TJAP96. DP96, DK96, DL96, 4 for 86/-. 



1A7GT 7/6 

1H6GT ?/8 

1N0GT 7/9 

1KB 6/6 



184 
185 
1T4 
3A6 
384 
3V4 

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SZ4G 7/6 
8/3012 11/9 
riALS 2/3 



lAm 

8AQ6 
8ATB 
8BA6 

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6CS6 
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6,'8 

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e/e 

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3; 8 



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7Cfl 
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10F1 



71- 
18/- 

m 

6/6 
8/6 
16/ 



I0P13 14 8 


DK32 7/9 


12AT7 6/9 


DK91 5/6 


12AU6 4/9 


DKW 9/3 


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DEW 7/- 


12AX7 4/9 


DL33 6/9 


12K8GT 7/6 


11L3I> i 1- 


20F2 10/6 


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2DL1 16/9 


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30C16 11/6 


eabcso e/e 


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EAF42 8/6 


30CI8 8 


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EBC33 7/6 


3 OF LI 18/6 


EBC41 8/- 


30FL14 18/6 


EBFB0 6/- 


30L16 14/- 


EBF89 8/3 


30L17 13,'- 


ECC81 8/9 


30P4 IB/- 


ECC82 . 4/8 


30P12 11/- 


ECC83 7/- 


30P19 18/- 


ECC84 56 


30PB1 18/6 


ECO J 4/9 


30 P LI 3 14/6 


ECF80 7/- 


30FL14 14/6 


ECF82 6/9 


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30W4 4/6 


ECH36 6/- 


3SZ4GT 6/- 


ECH4S 10/- 


6063 18/0 


ECH8I 6/8 


AZ31 8/- 


ECHB4 7/3 


B36 4/9 


ECL.-o S/9 


B7S9 18/6 


ecl82 e/e 


CCH36 10/- 
DAC32 7/3 


ECL58 8/3 


DAF9I 8/9 


EF39 8/8 


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DCC90 8/6 


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DF33 7/B 


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DF91 8/9 


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DF96 8/- 


EF69 6/3 


DH77 4/- 


EF91 8/8 


DB81 12 6 


EF9J 7/6 



EF183 8/6 
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EH90 



EL33 
EL41 

ELS 4 
KL90 
EL96 



EH34 13/9 

KM Hi 6/8 



EM51 
EMS* 
EM 87 
EY61 
EY86 
EZ40 
EZ41 
EZ80 
EZS1 
GZ32 
KT61 



KT81 Iff 
N7B 14/8 



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PCS* 
PC97 8/6 
PC900 8/- 
PCC84 6/- 
PCC89 10/8 
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PCF80 7/- 
PCF82 61- 
PCF86 9/9 
PCF800 11/6 
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PCF805 9/- 
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PCF80818/6 
PCL82 7/3 
PCL83 9/- 
FCL84 7/8 



PCL85 8/8 
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FE.N36C16/- 

!'i L^COIH 
PL36 9/3 



PL81 
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FL83 
PL84 



PUS00 18/- 

FX25 10/6 

FY 32 10/- 

PY33 10/- 

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PY81 
PY8U 
PY83 
PY88 



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B19 



6/6 

12:9 

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13 8 
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m 
s/e 

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L'CFSO 8/3 



rcu« 9/9 

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vCLsa 9/8 

CP41 10/6 



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UF89 
UL41 



?/- 
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UL44 »/- 

UL84 88 

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UY80 6/6 

VP4B 18/6 
VF1321 81/- 

Z77 3/8 



TrsniJlWrj 
AC107 10/- 
AC127 6/- 
AD140 16/6 
AP102 18/- 
AF116 6/- 
AP116 
AF117 
AF11B 
AF124 
AP12S 
AP126 
API 27 



0C22 
OC25 
OC26 
OC44 
OC46 
OC71 
OC72 
OC76 
OCS1 



6/6 

6/- 
3/6 
7/6 
7/8 
71- 
71- 
9/9 
8/6 
B/- 
3/1 
3/3 
8/6 
4/8 
6/8 
8/8 



OCS1B 8/3 

OCS2 6/9 

OC82D 6/- 

OC170 6/- 



READERS RADIO (P.E.) 

85 TORQUAY GARDENS, REDRRIDQE, ILFORD 
ESSEX Tel. 01- 5SO 7441 

Postage on 1 valre 9d. extra. On 2 valves or more, postage fld. per 
valve extra. Any Parcel Insure si against Damage In Transit fid. extra. 



HIGH SPEED MAGNETIC COUHTEBJ <4 X 1 X 
lin.). 4 digit. 12/24/48V. (state which) 8/6 each, 
P. A P. 1/-- 

C0PPEB LAMHIATE BOARD C8| X OS X iVIn.J. 
8/6 each. 5 lor 10/-. 

RE-SETTA8LE HIGH SPEED COUNTER 
(3XIX Jin.) 3 digit. 12/24/48V. (state wbichl 82/6 
each. 

BULK COMPONENT OFFERS 
100 Capacitors 50pF to -SirF. 
2o0 Carbon Resistors J i- iW. (Transistor types). 
250 Carbon Resistors 1 & ]W. 
100 Ceramic Capacitor!! 2— lOOOpF, 
25 Yitreona W/W Reguttors (5 D i,). 
12 Precision Reilstors (-l t 'o several standard valoes 

Included). 
25 Close Tolerance Caps. (2%). 
12 Silicon Diodes 500 pi. v. 750 m.a. 
4 Silicon Recta. 400 p.l.v. 3 amp. 
8 Silicon Rects. 100 p.i.v. 3 amp. 
50 Silicon Trans, (2X70(5.708, BHY28/29, BCY 41/42 

types.) rnmaried. Untested. 
60 Silicon Diodes 200 m.a. 100 p.i.v. Sub. Hln. 

ANY ITEM 10/-. ANY 5 ITEMS 12. 



S.C.Ri. (Thvristors) CRS1/20 5 6; CR81/40 7/6; 
CR83/10 7/6; CRS3,'30 8/8: CRS3'40 10/-; CRSSieO 
12/6 each. 

'3000' TYPE BELAYS {ex. new equip.) 10 for 25'- 
(onr choice) p.p. 5/-. 

PATTRICK & KINNIE 

Bl PARK LANE 

ROMFORD, ESSEX 

ROMford 44473 



BATTERY ELIMINATORS 

The ide»l way of running your TRANSISTOR 
RADIO, RECORD PLAYER, TAPE RECORDER, 
AMPLIFIER, etc. Types available: 9v; 7iv;6v; 
4|v (tingle output) 39/6 each. P. & P. 1/9. 
9v + 9v; 6v +6v:or4iv + 4Jv (two sepirjte 
outputs) 42/6 each. P. A P. 2/9, Please state 
output required. All the above units are 
completely isolated from mains by double 
wound transformer ensuring 100". safety. 

"** C.S. PRODUCTS (RADIOl LTD. 
(Dept. P.E,). 31 Oliver Road. London. E.I' 



The ELECTRONIC MUSICAL 
INSTRUMENT MANUAL 

New 5th Edition. 
By Douglas. 55/-. P. & P. 1/6. 

COLOUR TV PAL SYSTEM, by Patchetc. 

40/-. P. & P. I/-- 

F.E.T. CIRCUITS, by Turner. 25/-. P. & P. 
I/- 

TAPE RECORDER SERVICING 
MANUAL, by Helfyer. 63/-. P. & P. 4/6, 

ELECTRONICCOUNTING, byMullard. 
27/4. P. & P. I/-. 

SILICON CONTROLLED RECTI- 
FIERS, by Lytel. 21/-. P. & P. I/-. 

PRACTICAL OCSILLOSCOPE HAND- 
BOOK, by Turner. 25/.. P. & P. I/-. 

HAVING FUN WITH TRANSISTORS, 

by Buekwalcer. 24/-. P. & P. I/-. 

SOLID STATE POWER SUPPLIES 
AND CONVERTERS, by Lytel. 20/-. 
P. & P. I/-. 

ELECTRONIC MOTOR CONTROL, 

by Lytel. 30-/. P. & P. I/-. 

TRANSISTORS IN LOGIC CIRCUITS, 

byAltes. 16/-. P. & P. I/-. 

Where possible 24-hour service guaranteed 

UNIVERSAL BOOK CO. 

12 Linii NEWPORT ST., LONDON, W.C.2 
(Leicester Square Tube Station) 



446 



nMRKET 
PLACE 

Items mentioned in this feature are usually 
available from electronic equipment and com' 
ponenc retailers advertising in this magazine. 
However, where a full address is given, 
enquiries and orders should then be made direct 
to the firm concerned. 

COMPONENTS 

The "Apollo" subminiature mer- 
cury switch available from Photain 
Controls Ltd., should prove very 
useful for trip or alarm circuits, and 
in a variety of other circuits such 
as communications, measuring and 
control equipment. 

Very similar in appearance and 
size to a transistor, the switch con- 
sists of a robust metal housing and 
contains high purity mercury. One 
electrode is the metal outer casing 
and the other the centre lead, The 
contacts are sealed in glass and filled 
with gas. The load current is 0.3 A at 
110V. 

When the switch is tilted at a 
minimum of 30 degrees from hori- 
zontal position the mercury moves 
and closes or opens the contacts, 
switching the supply on or off as 
required. When operating there is 
no clicking noise. Further details 
are available from Photain Controls 
Ltd., Randalls Road, Leatherhead, 
Surrey. 

Now to lighting, the Mark-A-Lite 
is a small halfpenny size disc which 
glows continuously in the dark, yet 
needs no electricity, mains, battery or 
recharging. The back of the disc is 
self-adhesive and is useful for marking 
the position of any small item that 
could be a hazard, or for locating 
objects in darkness. Light switches, 
keyholes, car ignition switches and 
front panel controls, are just a few 
of the applications that come to mind. 

The Mark-A-Lite costs 1 1 s 4d and is 
available from Wrights Aviation Co. 
Ltd., 4 Melbourne Close, Morton, 
Middlesbrough, Yorkshire. 

A new range of battery holders 
have just been announced by A. F. 
Bulgin & Co, Ltd., Bye Pass Road, 
Barking, Essex. These holders take 
U2 cells and equivalents. They are 
designed for front panel mounting, 
making it easy to replace exhausted 
batteries; all contacts are heavily 
plated to prevent corrosion. 

The holder is fixed to a panel by 
four 6B.A. bolts, the front cap or 
contact being a push and twist 

An r.f. microminiature coaxial 
connector by Thorn Special Products 
is available for matched impedance 
coupling of 50 ohm screened cables. 
It is made of gold plated copper 
alloy, with crimped connections, 
the connector being insulated with 



p.t.f.e. The contact resistance is 
claimed to be less than 4 milli-ohms. 
This connector is supplied as a 
complete cable assembly, the pin 
and socket each being assembled 
with a 12in length of 50 ohm cable. 
Alternative lengths are available to 
order. 

EQUIPMENT 

Newmarket Transistors Ltd., have 
recently added a preamplifier to 
their range of "packaged circuit" 
modules. The PC 10 is intended 
mainly for tape head amplification 
and is powered from a 9V supply. It 
has an input impedance of 150 ohms 
and output impedance of 3.300 ohms. 
The sensitivity is given as 1 50mV out 
at 1kHz for a 15mV input. 

Readers thinking of purchasing a 
new multimeter may be interested 
in the Sanwa range available through 
Household Electrix Ltd., 47-49 High 
Street, Kingston-upon-Tbames, 

Surrey. 

The price of the Sanwa range of 
meters varies from £3 7s 6d to £1 3 5s. 

One item not shown at this year's 
Audio Fair is the Dewtron New 
Dimensions sound effects amplifier. 

Marketed at 8 guineas, plus 4s 
postage, by D.E.W. Ltd., Ringwood 
Road, Ferndown, Dorset, the unit 
provides adjustable echo, vibrato, 
spacial (reverberation) and tonal 
effects. The unit can be used with 
any domestic radio, record player, 
electronic musical instrument, or 
tape recorder having provision for 
an external speaker. 

The effects amplifier creates a 
pseudo "stereo" effect if an extra 
speaker is used together with the 
existing appliance speaker. The 
power output is approximately I watt. 
Another version is obtainable for car 
radio use and is wired directly to the 
car battery. 

AGENTS 

Home Radio (Components) Ltd., 

187 London Road, Mitcham, Surrey, 
have been appointed retail stockists 
of all Lektrokit components. 

Over 150 individual items in the 
Lektrokit ranges are now available 
"off the shelf" and are all obtainable 
through the postal delivery service 
run by Home Radio. 

Single cell or small quantities of 
Voltabloc rechargeable nickel- 
cadmium battery cells can now be 
purchased through Electroniques, 
Edinburgh Way, Harlow, Essex. 




Microminiature coaxial connector 
produced by Thorn Specie?/ 
Products 



Apollo mercury switches from Photain 

Controls 




Panel mounting battery holder by 
A, F. Bulgin 




Wrights Aviation Mark-A-Lite 




Dewtron New Dimensions 
sound effects unit maufactured by D.E.W. Ltd. 



447 




n^ 



A SELECTION FROM OUR POSTBAG 



Thriving and active 

Sir — About a year ago, a letter was 
published in your magazine, announ- 
cing the intention of forming a radio 
club in South London, The Addis- 
combe Amateur Radio Club was 
formed, having as its hard core several 
young people who wrote to us as a 
result of reading about us in P.E. 
Since those early days we have had 
many more members and visitors 
attracted by the publicity you have 
given us. The members have asked 
me, as secretary, to write to you with 
our thanks for the help and encourage- 
ment you have given to us, and 
doubtless to many other clubs who 
are struggling to get firmly established. 
Thanks to P.E. the Addiscombe 
Club is now a thriving and active 
club. 

S. V. Knowles, Hon. Sec, 

West Croydon, 

Surrey. 



Unsociable or mere 
handmaiden? 

Sir — I wonder how many readers have 
stopped to think how Electronics, as 
an activity for Amateur enthusiasts, 
has never produced a social move- 
ment for the advancement of its 
aims and interests in a similar way, for 
instance, to the Amateur Radio 
Movement. It might be said that 
this lack of an effective Club or 
Society movement is due to the lack of 
incentive to co-operate with other 
fellow enthusiasts, which is essential 
in such activities as Amateur Radio. 

It must mean that thousands of 
Electronics enthusiasts are working 
away on lonely projects, and that 
Electronics has no collective voice or 
recognisable unity as a hobby move- 
ment. 

But, a closer look at my statement 
about lack of incentive above, shows 
that it does not hold water. There 
are a great number of Amateur 
Movements with strong collective 
organisations, the Amateur Astron- 
omers, Model Engineers and Aero- 
modellers, to name just a few. None 
of these activities can claim an essen- 
tial social element, like that necessary 
for Amateur Radio, yet they have 
strong society movements. 

There might be more serious 
reasons for the lack I have been 



discussing. Is it possible that, on 
the average, Electronics enthusiasts 
are an unsociable type of person 
anyway, rather dealing with gadgets 
and things than with people? They 
may have had a strong desire to 
retreat into their gadgetry world, 
over which they can keep a sense of 
power. 

There is one further explanation, 
and that is the one that says Elec- 
tronics has no separate existence. 
This means that the activities of the 
people engaged in electronics are 
catered for by other firmly established 
bodies. Therefore, Radio Amateurs 
constitute a vast number of elec- 
tronics men. There is a large pool 
in the model control field. The Radio 
Astronomers make up another quite 
advanced group. The Photographer 
would build his timers and gadgets, 
without the need to go to an Elec- 
tronics Club. 

It would seem that Electronics is a 
handmaiden to other interests, in 
other words it has come too late and 
the prospects for any representative 
Society arising is bleak ... or is it? 
There may be readers with other 
views, but* the evidence would have to 
be strong! 

R. F. Marchant, 
Leyton, E.10. 



<( 



Phial "-ed 



Sir — I would like to congratulate 
A. J. Nicholls on his approach to 
Electronic and Mechanical car pro- 
tection (see Readout April issue). 
I feel though that his car is still 
dangerously vulnerable to theft. 

The modern thief, having beaten 
the electronics and entered the car, 
thinks nothing of breaking or . un- 
locking any mechanical device linking 
steering to a pedal. 

I have made my car safer by arrang- 
ing in addition, that the release of the 
handbrake, as the thief goes to drive 
away, breaks a glass phial and fills 
the car with tear gas. At this stage 
I felt my car was fairly secure until I 
realised that the thief might have a 
gas mask with him. 

I have therefore arranged things 
further so that as soon as the car 
moves forward small bursting charges 
in the hubs blow off all four wheels. 

Dr. R. Parfitt, 
London, S.E.19. 

You must have a thriving practice. We 
hope you don't charge a consulting fee 1 



Simplicity is the key 

Sir — I have read your Editorial in 
the April issue of Practical Elec- 
tronics with great interest. 

As the Design Engineer of a small 
firm of Instrument Engineers I too 
have found that some of the circuits 
given in your magazine tend to be a 
little too sophisticated. Of course, 
if the aim is to generate an increased 
interest in electronic circuitry this is 
very fine. If, on the other hand, 
usefulness is the aim I would suggest 
that simplicity is the best policy. 

Many manufacturers of instru- 
mentation have the tendency to 
make their products with many 
"frills" built into them as sales 
gimmicks. For instance, I know of 
one s.c.r. control circuit containing 
no less than ten transistors. Com- 
pared with another (fool-proof and 
accurate) circuit produced by another 
firm that only employs three 
transistors. 

There are numerous examples of 
this kind to be found in the industrial 
field. Believe me, the simpler a 
circuit can be made the less trouble 
in maintenance and reliability is to 
be expected. 

Trusting that these remarks may 
interest your readers. 

D. H. Heppell, 
War ley. 



Any square wire? 

Sir — Can any reader suggest a source 
of SQUARE connecting-up wire, 
as used in the early 1920's? 

This is urgently wanted by members 
of the Peterborough Radio and 
Electronic Society, in the making of 
"genuine 1922" wireless receivers 
for their "Radio Museum". Plenty 
of old components have been collec- 
ted—but not a bit of SQUARE wire. 
D. Byrne G3KPO, 
Jersey House, 
Eye, Peterborough. 

Come and join us 

Sir — We are writing to enquire if 
any of your readers in the Paddington 
area would be interested in visiting 
the Paddington and District Amateur 
Radio Society which meets every 
Thursday at 7.30 p.m. 

The club promotes an interest in 
amateur radio and allied subjects. 
Lectures and film shows are amongst 
the itinerary together with a con- 
structional evening, held on 
Wednesdays. 

The Clubroom is in the Beau- 
champ Lodge Settlement, 2a Warwick 
Crescent, W.2. 

The Club intends to hold several 
field days during the year and provide 
demonstration stations for local 
events 

M. M. Pawley G8AWV, 
London, W.2. 



448 






LIMITED 



TRANSISTORS PRICE 



AC 107 

AC I 26 

ACI27 

ACI2B 

ACYI7 

AFI 14 

AFII5 

API 16 

AFI 17 

AFI IB 

AFII9 

AFI 78 

BCZII 

BFY50 

BSY25 

SSY26 

BSY27 

BSY28 

BSY29 

BSY95A 

OC4I 

OC44 

OCM5 

OC7I 

OC72 

OC73 

OC8I 

OC81D 

OC83 

OCI39 

OCI40 



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m 


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ffr 


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3/. 


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a/* 


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2/6 


AAY42 


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EXCITING NEW PAKS FOR AMATEURS, 
PROFESSIONALS, FACTORIES. ORGAN 

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USE LARGE QUANTITIES OF TRANSISTORS, 

XA PAK 

Germanium PNP type transistors, equivalents to 
* large part of the OC range, i.e. 44, 45, 71, 72, 
81, etc, 

PRICE £S PER 1000 



XB PAK 

Silicon TO-18 CAN typt transistors NPN/PNP 
mixed lots, with equivalents to OC200-I, 2N706a, 
BSY27/29. 

PRICE £3.5.0 PER 500 

PRICE f 10 PE* 1000 

XC PAK 

Silicon diodes miniature glass types, finished black 
with polarity marked, equivalents to OA200, 
OA202, BAY3I-39 and DKIO, etc. 
PRICE £5 PER 1000 

ALL THE ABOVE UNTESTED PACKS HAVE 
AN AVERAGE OF 75% OR MORE GOOD SEMI- 
CONDUCTORS. FREE PACKS SUSPENDED 
WITH THESE ORDERS, ORDERS MUST NOT 
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TRANSISTORS ONLY1/- EACH 



SILICON 



PLANAR 



All these types available 

2N929 2N706 2SI3I 2SI03 

2S501 2N706A 2S5I2 2SI04 

2N24II 2N30II 2SI02 2N2220 



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2N696 2NI6I3 
2N697 2NI7II 
2NI507 2N1893 
unmarked. 



• P.N.P 

2S733 BFYI0 
2N726 2S73f 
2N2906 2S732 



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Manufacturers over runs for the new PRE-PAK range. 



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crosses m ^„ rs etc L.i- 
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.NPNSMicon TRANSISTORS 10/- 



*n 1000 PIV 1 amp. 
■ u Min. Silicon 



DIODES 10/ 



9c BSY26-27 
£a NPN Silicon 



TRANSISTORS 10/- 



lf| 10 Wall Silicon 
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25 NPN^t'ikon TRANSISTORS 10/- 



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NpKcor. TRANSISTORS 1 P./'. 



mn 1N9U-6 

** u Sub. Min. Silicon 



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igh Quality 



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PRE-PAK. N.60S POWER 
TRANSISTOR EQUIVALENT 
TO NKT30I-4 



5/- each 



TANTALUM CAPACITORS 



4/- each 



NEW UNMARKED UNTESTED PAKS 






PRE- PAKS 

No. Price 

A I 6 Silicon rectifiers BY 100 type - 10/- 

A3 20 Mixed marked and tested tram, - 20/- 
AI3 25 New trans. & diodes marked & tested 20/- 

A15 2 Power Comp. Pair. AD 16 1/2 - 20/- 
AI7 3 Sil. stud recs. 6 amp. 400 PIV. 

BYZI2 - 20/. 

AI8 2 Sil. scud recs. 10 amp. 800 PIV. - 20/- 



B! 50 Unmarked untested, trans,, new 

Mixed Types - 10/- 

E2 4 Solar cells, inc. Book of Instructions 10/- 

B3 4 OA5 gold bonded, diodes Mullard - 10/- 
BS 7 Matched set, QG44.45/8 ID/81 - 

diode - 10.'- 
B6 IS Red spot AF. trans, or white spot 

RF 10/- 

BB 2 Power trans. OC26/35 type - 10/- 

B9 I Light sensitive cell, ORPI2 type - 9/- 

BI0 10 50V trans, germ. PNP latest type - 10/- 

B44 I Tunnel diode. AEYII, 1050 Mc/s - 10/- 

B2I 2 Sil. recs. 10 amp., 50-100 PIV - 10/- 
845 t Power trans. ADY22/TK400A 

VCB60 ICSAmps. PNP - 10/. 
B49 2 Power trans. GET 9 VCB64 IC 8 amp. 

germ. PNP - 10/- 

866 150 — Germanium diodes, untested 10,'- 



C2 I Unijunction. 2IM2160 or 2N2646 • 15/- 
C4 2 RF power trans,, OC22 andBUYII - 15/- 
CI5 4 Silicon PNP trans, in the 2S300 Series 15/- 
C31 4 Sil. recs- 8C0 PIV £ amp. top hat - IS/. 
C32 2 Power trans. TK400A/NKT4Q4 

VCB64 IC8 amc 15/- 

70 amp. 400 PIV SCR special offer 70/- 



IN TEG RATED CIRCUITS (TEXAS) 

SN7430 8l NX p G°AT r ri9/6 



Make a Rev. Counter for your Car. The 
TACHO BLOCK'. This encapsulated block 
will turn any 0-1 mA meter into a perfectly 
linear and accurate rev -^%^^ / 
counter for any car. Mm !/-_. I. 

State 4 or 6 cylinder. £m\JI 68011 



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TANTALUM CAPACITORS, 

TRANSISTORS, RECTIFIERS 

& CIRCUIT DIAGRAMS, 

SUBSTITUTION CHART 



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AIRMAIL. 



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•T 



I 



DEPT. A, 222-224 WEST ROAD, WESTCLIFF-ON-SEA, ESSEX 
TELEPHONE: SOUTHEND (0702) 46344 



Practical Electronics Classified Advertisements 



The pre-paid rate for classified advertisements is 1/3 per word (minimum order 15/-), box number 
1/6 extra. Semi-displayed setting £4 . 2 . 6 per single column inch. All cheques, postal orders, 
etc., to be made payable to PRACTICAL ELECTRONICS and crossed " Lloyds Bank Ltd." 
Treasury notes should always be sent registered post. Advertisements, together with remittance, 
should be sent to the Classified Advertisement Manager, PRACTICAL ELECTRONICS, 
George Newnes Ltd., 15/17 Long Acre, London, WC2, for insertion in the next available issue. 



SERVICE SHEETS 



■ERVICE SHEETS, Radio, TV, 5000 models . 
List 1/«. S.A.E. enquiries. TELRAY, 11 
Maudland Bank, Preston. 



RADIO TELEVISION, over 8,000 Models. 
JOHN GILBERT TELEVISION, lb Shep- 
herds Bush Rd., London, W.6. SHE 8441, 



.SERVICE SHEETS. RADIO, TELEVISION, 
TAPE RECORDERS, 1925-1868, by return 
post, from 1/- with free fault -And ins guide. 
Catalogue 6,000 models, 2/S. Please send 
stamped addressed envelope with all orders/ 
enquiries. HAMILTON RADIO, 54e London 
Road, Hexhill, Sussex. 



WANTED 



VALVES WANTED, brand new popular 
types boxed. DURHAM SUPPLIES (E), 
175 Durham Road, Bradford 8, Yorkshire. 



EDUCATIONAL 



STUDY RADIO, TELEVISION AND ELEC- 
TRONICS with the world's largest home study 
organisation. I.E.R.E,; City & Guilds; 
R.T.E.B., etc. Also practical courses with 
equipment. Xo books to buy. Write for 
FREE Prospectus to ICS (Dept. 577), Intertext 
House, London, SW11. 



ENGINEERS. A technical certificate or 
({Ualifkatiou will bring you security and much 
better pa v. Elem, and adv. private postal 
courses for C.Kng., A.M.I.K.H.E., A.M.S.E. 
{Mech. it Elec), City ft Guilds, A.M.I.M.I., 
A.I.O.B. and G.C.E. exams. Diploma courses 
in all branches of Engineering — Mech., Klec., 
Auto, Electronics, Radio, Computer*, 
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for FREE 132-page guide. BRITISH 
INSTITUTE OF EXfilXEKRlXU TECH- 
NO LOG V (Dept. 125K), Aldermaston Court, 
Aldcrmnstou, Berks. 



SET INTO ELECTRONICS — big opportunities 

for trained men. Learn the practical way with 
low-cost Postal Training, complete with equip- 
ment A.M.I.E.R.E., R.T.E.B., City & Guilds, 
Radio, '17 V, Telecoms., etc. For FREE 100- 
page book, write Dept. 850K, CHAMBERS 
COLLEGE, 148 Holborn, London, E.C.I. 



RADIO OFFICERS see the world: Sea going 
and shore appointments. Trainee vacancies in 
September. (irants available. Day anil 
Boarding students. Stamp for prospectus. 
WIRELESS COLLEGE, Colwyn Bay, Wales. 

SITUATIONS WANTED 



A YOUNG ELECTRONICS enthusiast is looking 
for a position as a trainee technician lit Radio, 
TV, etc. Prepared to work hard. Please reply: 
Box 11. 




SITUATIONS VACANT 
RADIO & TELEVISION SERVICING 
RADAR THEORY & MAINTENANCE 

Vacancies regularly exist in industry for men with good knowledge 
of Radio TV and Radar. Our one-year day courses provide 
effective training. Shorter day courses available for men with 
experience. Write for details to: — 

The Secretary, London Electronics College, 20 Penywern 
Road, Earls Court, London, S.W.5. Tel. 01-373 8721 



A.M.I.E.R.Ii.. A.M.S.E. (Elec), City A 
Guilds, G.C.E. , etc., on "Satisfaction or Refund 
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state subject of interest. BRITISH 
INSTITUTE OF ENGINEERING TECH- 
NOLOGY (Dept. 124K), Aldermaston Court, 
Aldermaston, Berks. 



YOUNG HAN required to assist in develop- 
ment department working on audio device* 
Apply SELMER ELECTRONICS LTD., 
40 Theobalds Road, W.C.I. Phone; 01-242 
0141. 




TECHNICAL TRAINING by 

IN RADIO, TELEVISION AND 
ELECTRONIC ENGINEERING 

First-class opportunities in Radio and Electronics await the I C S trained man. 
Let I C S train YOU for a well-paid post in this expanding field, 
I CS courses offer the keen, ambitious man the opportunity to acquire, quickly and 
easily, the specialized training so essential to success. Diploma courses in Radio/ 
TV Engineering and Servicing, Electronics, Computers, etc. Expert coaching for: 

* INSTITUTION OF ELECTRONIC AND RADIO ENGINEERS. 

* C.ft G. TELECOMMUNICATION TECHNICIANS 1 CERTS. 

* C.8.G. ELECTRONIC SERVICING. 

• R.T.E.B. RADIO AND TV SERVICING CERTIFICATE. 

• RADIO AMATEURS' EXAMINATION. 

• P.M.G. CERTIFICATES IN RADIOTELEGRAPH Y. 

Examination Students Coached until Successful. 

NEW SELF-BUILD RADIO AND ELECTRONIC COURSES 

Build your own 5-valve receiver, transistor portable, signal generator, multi- 
meter and valve volt meter — all under expert guidance. 

POST THIS COUPON TODAY and find out how I C S can help YOU in your 
career. Full details of I C S courses in Radio, Television and Electronics will be 
sent to you by return mail. 
MEMBER OF THE ASSOCIATION OF BRITISH CORRESPONDENCE COLLEGES 



INTERNATIONAL 

CORRESPONDENCE 

SCHOOLS 



A WHOLE WORLD 

OF KNOWLEDGE 

AWAITS YOU 1 



International Correspondence Schools 

(Dept. 152), Intertext House, Parkgate Road, 

London, S.YV. 1 1 . 



NAME 



Block Capitals Please 



ADDRESS 



... 6.68 



450 



I 



20 Penywcrn Road, Earti Court, London S.W.5. 



Tel. 01-373 3721 



This Private School provides full and part day training in the 
following professional subjects '" 

RADIO & TELEVISION SERVICING 
RADAR THEORY & MAINTENANCE 
RADIOTELEGRAPHY 



MISCELLANEOUS 



CALL OR SEND fur list from the most interest- 
ing shop in Lancashire. Electririil Mech- 
anical and Electronic Goods. .ROGERS, 31 
Xelson Street, fioutliport. 



ARTIFICIAL LIFE 

Well almost, because the NEW range of 
projects include; an electronic 'animal' 
which LEARNS, and a device capable of 
REPRODUCING itself! Other projects 
SURE TO INTRIGUE YOU ire an audio 
transmitter/ receiver which has quite an 
amazing range and requires NO LICENCE; 
also a machine which recognizes itself, and 
an electronic dog whistle, etc., etc, HOSTS 
OF EASY-TO-CONSTRUCT projects. 
SEND 2/6 for our list of 'BOFFIN 
PROJECTS'— NOW! 

To: 'BOFFIN PROJECTS* 
4 CUNLIFFE RD. 
STONELEIGH 
EWELL 
SURREY 



"PRACTICAL ELECTRONICf . Homrcom. 
Rhythmic: Effects Unit. Impact Counter. 
Fluorescent Camping Light. Giissundovibe. 
■Spring Line Reverberation I'nit, I.C. Tape 
Recorder. Cmnbotron. Analogue Computer. 
Photographic Kxposure Meter. Water Level 

Harm. Pukz Bos, Yodeller Door Monitor. 

.C. Gram Amplifier. Thyristor 1'mver Con- 
iller. Translator Millivoltmeier. Screenwiper 
Delay I'nit. Investigator Oscilloscope. C.R.O. 
Trace Doubter. Light Operated Stopwatch. 
ixiniity Detector. Phototlash Slave Unit. 
Integrated Stereo Amplifier and all con- 
structional projects going back to Issue 1. 
Send s.a.e. for Your choice of itemised price 
list*. A.TAX ELECTRONICS, 18a Itumhold 
Koad, Fulhain, Loudon, S.W.6. 



BOOKS AND PUBLICATIONS 



SURPLUS HANDBOOKS 

19 set Circuit and Notes 5/6 P.P. 6d 

1 155 set Circuit and Notes 5/6 P.P. 6d 

H.R.O. Technical Instructions . . 4/6 P.P. 6d 
38 set Technical Instructions. . , . 4/6 P.P. 6d 
46 sec Working Instructions .... 4/6 P.P. 6d 
SB set Technical Instructions. .. . */- P.P. fid 

BC. 221 Circuit and Notes 4/6 P.P. 6d 

Wavemeter Class D Tech. Instr 4/6 P.P. 6d 

18 set Circuit and Notes 4/6 P.P. 6d 

BC.I0O0 (31 set) Circuit & Notes 4/6 P.P. 6d 
CR.100/B.2B Circuit and Notes 9/6 P.P. 9d 

R.I 07 Circuit and Notes , . «/- P.P. 6d 

A.R.88D. Instruction Manual 16/- P.P. 1/6 

62 set Circuit and Notes ...... 5/6 P.P 6d 

52 set Sender* Receiver Circuits 7/6. post free 
Circuit Diagrams 4/- each post Tree. 
R.II16/A, R.I224/A, R.1355, R.F. 24, 25, & 26. 
A. 1134, T.I 154, CRJ00. BC.342. BC.3I2. 
BC.348.J.E.M.P. BC.624. 22 set. 
Resistor colour code indicator, II- P.P. 6d. 
S.A.E. with all enquiries please. 
Postage rates apply to U.K. only. 
Mail order only to : 

Instructional Handbook Supplies 

Dept. P.E., Talbot House, 28 Talbot Gardens 
Leeds 8 






TAPE RECORDERS, TAPES, ETC. 



20% CASH DISCOUNT on most famous makes 
of Tape Recorders, Hi-Fi equipment, Cameras, 
etc. Join England's largest Mail Order Club 
now and enjoy the advantages of bulk buying. 
Send 5/- for membership card, catalogues, 
price lists and ask for quotation on anv item. 
C.B.A. (Dept. A 18), 370 St. Albans Road, 
Watford, Herts. 



TAPES TO DISC — using flnest professional 
equipment — 45 r.p.m. 18/-. S.A.E. leaflet. 
TJEROY, High Bank, Hawk Street, Carnforth, 
Lanes. 



FOR SALE 



BRASS, STEEL, LI6HT ALLOY, STAINLESS 
STEEL TUBE. Bar Material, Tools, Mechan- 
ical, Electrical, plus Assorted Lots. Send 
S.A.E. for latest Cat. of 1,000 items. K. R. 
WHISTOX, Dept. BPE, New Mills, Stockport. 



ENTHUSIASTS! Discover the fascinating 
world of model railway signalling! Send for 
details of Conrad model railway control panels, 
1/- post free from COCK ROBIN CONTROLS, 
:iti Vllliers Avenue. Surbiton, Surrev. 



EXCLUSIVE OFFER 

Further to our overwhelming response to 
our recent advert, we have acquired another 
consignment of extendable 4 core leads, ex- 
tends from I ft to 6ft 6m as supplied to G. P.O. 
for telephones. These have many applications 
in the field of amateur electronics, etc. 
These are offered to you at the unbeatable 
Price of 5/- each or 55/- for 12 Post Free. 



PAXOLIN 5HEETS 
I Sins x I2ins sheet 
4/6d. or ^d. per sq. 
inch cut to size. Post 
Free. 



PRINTED CIRCUIT 
BOARD 

Sins X ISiins sheet 
6. Od. or Id. per sq. 
inch cut to size. Post 
Free. 



larger sixes available upon request 

at Specialfy reduced prices. 

Mason Trading Company 

24 Stephen Street, Coventry 



100 PACE illustrated Catalogue Xd. 17 
Government and manufacturers' electronic 
surplus, also new section of latest semi- 
conductors and miniature components. Credit 
voucher for 2/6 included. Price 3/- post free. 
ARTHUR SALLIS LTD., 93 North Road, 
Brighton, 



Operational Amplifiers for PEAC 
Analogue Computer, ready built on 
PC board, tested and guaranteed, 
34/- each. 
Kits available at 28/- post free. 

WESTEK ELECTRONICS 

10 Maple Lodge Close, Maple Cross 
Rickmansworth, Herts, 



FOR SALE (continued} 



USl 



|r[l>I--T- 



X. 




HAMMERED ENAMEL 

MAKES FANTASTIC DIFFER- 
ENCE TO PANELS— say hun- 
dreds of enthusiastic users. 'Crackle' 
pattern appears like magic on wood 
and metal. No undercoat. Air 
dries 15 min. to hard 
glossy finish. Heat, 
liquid & scratch- 
proof. Lt. &Dk. 

Blue; Bronze; Silver; Green; Black. ■»»«• ,„,- 
NOW for trial ipt. Tin. Col. samples & instn's. 
Post free. 

FINNIGAN SPECIALITY PAINTS Dept. P.E. 
STOCKSFIELD. Tel. 2280 Northumberland. 



BRUSH 
SPRAY-ON 
Send 107- 



MORSE 



MADE 
EASY 



!! 



FACT NOT FICTION. It you start RIGHT 
you will be reading amateur and commercial Morse 
within a month (norms I progress to be expected). 

Uelog scientifically prepared 3-apeed records yon 
automatically learn to recognise the code RHYTHM 
without translating. You can't help It, It's is easy as 
learning a tune. 18 W.P.M. In 4 weeks guaranteed. 

For details and course C.O.D. ring 3.T.B. 01.660 289o 
or send Sd. stamp for explanatory booklet to; 

83CHS/H. 45 OREEN LANE,' FURLEY, SURREY 

RECEIVERS AND COMPONENTS 



BARGAIN PARCELS of new surplus Elec- 
tronic Components, 2/6, 5/-. 10/-, post free. 
DOLPHIN ELECTRONICS, 5 Pooles Way, 

Briar Close, Burnt wood, nr. Lichfield. 



NEW PRICES ON 
NEW COMPONENTS 

ELECTROLYTIC CAPACITORS (Mullard) 

8;iF/4V, 6-4/iF/64V, 4/jF/IOV, 2-5/iF/l6V, I eaF/JSV, 
lnF/40V. 64;jF/64V. 1/6. 32uF/4V. 25uF/6-4V. 
I6^F/I0V, luuF/l6V, 64iiF/2SV, 4/iF/40V, 25^F/ 
64V. 1/3. 64,2F/4V, 5Q/jF/6-4V, 12^F/JQV, 20nF/l6V, 
I2-5^F/25V, 8mF/40V. 5/iF/64V, 1/2. l25aF'4V, 
IOOnF/6-4V, 64uF/l0V, 40/iF/l6V, 25uF/25V, I6uF/ 
40V, 10^F/64V, 1/-. 250uF/4V. 2CKVF/6 4V. I25*iF/ 
10V, 80uF/l6V. SOfjFflSV, 32£tF/40V, 20pF/64V, 
l/l, 400nF/4V. 320nF.'64V, 200pF/IOY, l25|iF/16V, 
80pF/25V, 50jjF/40V, 32*ir764V. 1/2. 

POLYESTER CAPACITORS (Mullard) 

Tubular, 10%, 160V: 1. 015, 0022uF, 7d. 
033, 047iiF, Bd, 068, 0-ImF. »d. OIS^F. ltd. 
Q22^F, I/-. O'33/iF, 1/1. 047uF, 1/6. 0-68uF, 2/J, 
1/iF, 2/8. 4O0V: 1,000, I ,SO0, 2,200, 3,300. 4,700pF, 
6d. 6,600pF, OOljiF, 0015, 0-022fiF, 7d. 003J/iF, 
8d. QQ47,uF, 9d. 0068nF, lOd, 0-|;iF, lid. 0-ISuF. 
1/2. 0-22^F, 1/6, 033pF. 2/1. 47^F, 2/8. 
Modular: metalliied, P.C. mounting, 250V; 
001, 0015. 0-022,. F, 7d. 0033, 0047,.F 8d. 068, 
00l*iF, 9d. OlSjiiF, lid. 0-22^F, I/-, 0-33uF. 1/5, 
0-47jiF, I /B. 68/jF, 2/3. f uf. 1/9. 

POLYSTYRENE CAPACITORS. 5%, 160V: 

10, 12, IS, 18, 22. 27, 33, 39. 47, 56, 68. 82, 100, 120, 
ISO, 180, 220, 270, 130, 390. 470, 560. 680. 820pF, 
5d. 1,000, 1,500. 2.200. 6d, 2,300, 4,700, S.600pF, 
7d. 6,800, 10,000, 8d. I 5,000, 22,OO0pF, 9d, 

POTENTIOMETERS (Carbon), miniature. 
I- xi- spindle. Lin. 100 Horizontal to I0M, Log. 5K 
to 5M.23. 

SKELETON PRE. SET POTENTIOMETERS 
(Carbon): Lin. I00O to 5Hn horiiontal and 
vertical P.C.M. mounting. 

MINIATURE (0 3W), )/-. Submin. 10-IW). lOd. 

RESISTORS (Carbon film): 5%, 10% over I M D. 

Range: 4-7 [1 to lOmMn. 

Power Series Price (Over 99) 

±W E24 Idea. (IJd. ea.) 

jW E24 lid. ea. (2d. ea.) 

100 off per value: iW, 13/9. £W, 15/6. 

C.W.O. P. A P., I/-. Minimum order value 5/-. 

DISCOUNT— 10% over £2. 15% over £5. 

Send S.A.E. For May 1968 Catalogue. 

DUXF0RD ELECTRONICS (PE) 

DUXFORD, CAMBS. 

Tel,: Saws ton 3031 



451 



RECEIVERS AND COMPONENTS (continued) 



RECORDING 
TAPES 

Fully Guaranteed 



7' DIP 
7* UP 



2,400* 19/- 

1,900' 12/1 

7* STO 1,200' 7/ J 

51* D/P 1,800' 14/» 

1 ,200' 91- 



St' UP 
sr STD 
S" D/P 
5' UP 
j* STD 
3" D/P 
3* UP 
4" D/P 



900' 6/6 
,200' 10/9 
900' 7/3 
600' 5/3 
185' 1/3 
225' V- 
300' 41- 
D/P Concorde 

3.000' 33/6 
Spool ■: 81', 6/3; 7", 

1/3: sr. i/-; s\ 2/-j 
3*. 9d, 

Post and Packing up to 3 
reefs 2/9 otherwise 4/6. 



OC22 81- 
OC23 ■'- 
OC25 6/6 
OC26 6/6 
OC28 6/6 
OC3S 6/6 
OC36 6/6 
OC44 1/- 
OC45 2/6 
OC46 17- 
OC70 31- 
OC7I 1/6 
OC72 1/6 
OC74 41- 
OC75 2/6 
OCSI 1/- 
OC8ID 31- 
OCB2D 3/- 
OCB2 3/- 
OC83 41- 
OCI70 41- 
OCI7I 4- 



OC202 
OA8I 

OAI82 
OA200 
OA202 
AC 1 07 
AC 126 
AC 1 27 
ACYI7 
ACYI8 
ACYI9 
ACY20 
ACY2I 
ACY22 
ADI40 
ADH9 
AFIM 
AFI 16 
AFII7 
AFZI2 
i BCY33 
I BCY34 



BCY38 5/6 
BCY39 5/9 
BCY70 6/6 
BCY7I 10/6 
BCY72 6/6 
BFX29 15/- 
BFYI8 5/- 
BFY19 
BFY50 
BFYSI 
BFY52 
8SY16 
BSY27 
BSY28 
BSY29 
BSY38 
BSY39 

BSY95A 4/6 
BY 1 00 4/6 
BYZI0 9/6 
BYZ1I S/- 
BYZI2 6/6 



5/6 
5/6 
5/6 
5/6 
4/6 
4/6 
4/6 
4 6 
4 6 
4,6 



Send S.A.E. for complete list. P. & P. 1/- 



A. MARSHALL & SON (London) LTD. 

28 Cricklewood Broadway, N.W.2 
Tel. 01-452 0161/1, Dept. P.E.I9 



BYZ!3 

GETI02 

GET 103 

NKT24I 

NKT242 

NKT244 

N(CT24S 

NKT26I 

NKT262 

NKT264 

NKT27I 

N KT603 

NKT6I3 

NKT674 

NKT677 

NKT7I3 



S/« 
41- 
41- 
6/6 
61- 
S/6 
5/6 
4/6 
4/6 
4/6 
4'6 
6/6 
6/6 
61- 
6/- 
5/6 



NKT734 


5f9 


NKT736 


6/6 


NKT773 


5/6 


NKT781 


61- 


2N696 


st- 


2N697 


si- 


2N706 


4/6 


2N706A 


4/6 


2N70B 


5/- 


2N2220 


5/- 


2N222I 


V- 


2N2222 


si- 


2N2369A 


8/7 


2N24I1 


6/6 


2N3053 


«/- 



VEROBOARDS: 3}" X 2j\ 1/6; 

3*" X H'. 4/1 j cutter, B/-. 

DEE GEE: 30 watt Soldering Irons, 

16/- each. 

SPEAKERS: 3 ohm. S". 14/6; 8' 

15/6; 12', 39/6; 7"x4", 16/6; 3", 9/6. 

RESISTORS; i watt.6d;j- watt, 6d. 
ELECTROLYTICS: I5v I MFD up 
to 100 MFD, 1/6 each. 



COMPONENTS 

POSTAL SERV1 CE 

* RECHARGEABLE 

BATTERIES 

(Sealed DEAC Ni-Cad) 
PP3 Equiv. ; 9v. 37/- (p. & p. 2/- 
U2 Equiv,: l.2Sy. 12/6 (p. & p. 2/- 
U7 Equiv.: l.2Sv. 11/- (p. & p. 1/6) 
Ull Equiv.: I,25v. 26/- (p. & p. 1/6) 

* BARGAIN PACK 

100 Hi-Stab Resistors 

30 Silicon Diodes ■ | 

8 Silicon Top Hat Rectifiers 

* ASSORTED RESISTORS— Hi-Stab. 300 off 
(5%, -^.i. ^watt, worth £3) ; 15/- 

(P. & P. 1/6 per order) C.W.O. 

S.A.E. for list of Industrial Components 

for the Home Constructor 

ELMBRIDGE INSTRUMENTS LTD. 

I. land Farm Avenue, West Molaiey, Surrey 




BI-PAK SEMICONDUCTORS 



DEPT El 



8 Radnor House 
93/97 Regenr St 
London W 1 



QUALITY-TESTED VALUE PAKS* BARGAINS 

2NI22S Germ. PNP 



2 Drift Trans .. 

lOOMc/s 10/- 

6 Matched Trans. OC44/45/8I/8ID 10/- 

16 Red Spot AF Trans. PNP ... 10/- 

16 White Spot RF Trans. PNP ... 10/- 

5 Silicon Rects. 3 A 1 00-400 PIV ... 10/- 

2 10A Silicon Rects. 100 PIV ... 10/- 

2 OC 140 Trans. NPN Switching ... 10/- 

1 I2A SCR 100 PIV 10/- 

3 5il. Trans. 2S303 PNP 10/- 

4 Zener Diodes 250mW 3-1 2V ... 10/- 
3 200Mc/s Sil. Trans. NPN BSY26/27 10/- 

3 Zener Diodes 400m W 33V 5% Tol. 10/- 

4 High Current Trans. OC42 Eqvt. 10/- 

2 Power Transistors I OC26 1 OC35 10/- 

5 Silicon Recti. 400 PIV 2S0mA ... 10/- 
4 OC75 Transistors Mullard Type... 10/- 

1 Power Tram. OC20 100V ... 10/- 
4 OA202 Sil. Diodes Sub-min. ... 10/- 

2 Low Noise Trans. NPN 2N929/30 10/- 

1 Sil. Trans. NPN VCB 100 ZT86 ... 10/- 

B OA81 Diodes ,, 10/- 

4 OC72 Transistors Mullard Type... 10/- 

4 OC77 Transistors Mullard Type... 10/- 

5 Metal Alloy Transistors Mat. Type 10/- 

4 Sil. Rects. 400 PIV 500mA ... 10/- 

5 GET884 Trans. Eqvt. OC44 ... 10/- 
S GET8B3 Trans. Eqvt. OC4S ... 10/- 

2 2N708 Sil. Trans. 300Mc/s NPN... 10/- 

5 GT4I/45 Germ. Trans. PNP Eqvt. 
OC7I 10/- 

3 GT31 LF Low Noise Germ. Trans. 
PNP ... 10/- 

6 IN9I4 Sil, Diodes 75 PIV 75mA ... 10/- 
8 OA95 Germ. Diodes Sub- min.... 10/- 

3 NPN Germ. Trans. NKT773 Eqvt. 
ACI30 10/- 

2 OC22 Power Trans, Germ. ... 10/- 

2 OC25 Power Trans. Germ. ... 10/- 

2 OC73 Mullard Trans 10/- 

4 AC 1 28 Trans. NPN High Gain ... 10/- 

2 AC 127/128 Camp, pair PNP/NPN 10/- 

3 2N 1 307 PNP Switching Trans. ... 10/- 

7 CG62H Germ. Diodes Eqvt. OA7I 10/- 

3 AFI 16 Mullard Type Trans. ... 10/- 
12 Assorted Germ. Diodes Marked.., 10/- 

4 AC126 Germ, PNP Trans. ... 10/- 
t ORPfil Photo-conductive cell ... 10/- 



4 Silicon Rects. 100 PIV 750mA ... 10/- 
3 AFII7 Trans. Mullard Type ... 10/- 

7 OC8 1 Type Trans. 10/- 

3 OCJ7I Trans, Mullard Type ... 10/- 
3 2N2926 Sil. Epoxy Trans. ... 10/- 

7 OC7I Type Trans. 10/- 

25 Trans. Heatsinks fit TO 18, SO 1 2, 
etc. ... 

2 2S70I Sil, Trans. Texas 

3 12V Zeners 400mW 

2 I0A 600 PIV Sil. Rects. 1S425R ... 

3 BC108 Sil. NPN High Gain Trans. 
I 2N9I0 NPN Sil. Trans. VCBIOO 

SOMc/s 

1 1,000 PIV Sil. Reet. ISA RS3I0AF 15,'- 
3 BSY95A Sil. Trans. NPN 200Mc!s 15/- 

3 OC200 Sil. Trans. Mullard 

2 Sil. Power Rects. BYZI3 
I Sil. Power Trans. NPN lOOMc/s 

TK20IA 

6 Zener Diodes 3—1 SV Sub-min. ... 
I 2N1I32 PNP Epitaxial Planar Sit. 

Trans. 

3 2N697 Epitaxial Planar Trans. Sil. 

4 Germ. Power Trans. Eqvr. OCI6 
Mullard 

1 Unijunction Trans. 2N2646 

2 Sil. Trani. 200Mc/s 60Vcb ZT83/84 
I Sil. Planar Trans. NPN lOOMc/s 

BSY25 SiV«4" 

I Tunnel Diode 1N3720 (TD5) G.E. 

1 Unijunction Trans. 2N2I60 TO-S 
j:an G.E 

2 Sil. Rects. 5A 400 PIV Stud Type 
2 Germ. Power Trans. OC2B/29 ... 
I E0A Sil. Stud. Rect. 800 PIV 

1 Tunnel Diode AEY1 1 l,OS0Mc/i 
STC 

2 2N2712 Sil. Epoxy Planar HFE225 
max. 

6 BY 100 Type Sil. Rects. 
15 Sil. and Germ. Trans. Mixed, all 

marked New 

10 New Power Trans. GEC replaces 

OCI6/26/28 

4 OAI0 Diodes Mullard 



FREE 



10/- 

1 0- 
10/- 
15/- 

15/- 



IS/- 
15/- 

15/- 
15/- 

15/- 
15/- 

15/- 
15/- 
15/- 

15/- 

m- 

1S/- 
15/- 

15/- 
U/- 

15/- 

15/- 
20/- 

30/- 

30/- 
10/- 



Oni 10/- Pack of your own 
choice fr«e with order* 
valued £4 or over. 



• TESTED DEVICES* 



ACI25 


IP 


AC 176 


5/6 


AFI 39 


10/- 


AFZI2 


10/- 


BC107 


5/- 


BCI08 


S/- 


BCI09 


5/- 


BCY33 


s/- 


BCY34 


6/- 


-BCZI0 


5/- 


BCZ1I 


6/- 


BFYS0 


71- 


BFYSI 


7/6 


BFY52 


7/6 


MAT] 00 


1/- 


MAT 120 


3/6 



NKT773 

NKT7B1 

OC44 

OC45 

STI40 

STI4I 

2N696 

2N697 

2NI090 

2N 1 306 

2N2I47 

2N2894 

2N38I9 

2N3820 

2S302 

2S303 

25304 



4/- 
5/6 
19 
t/» 
1/- 
41- 
4/6 
3/- 
4/9 
4/- 
15/- 
•/- 
15/- 
15/- 
5/- 
4/- 
6/- 



Set of 4 trans, comp. with 
circuit and building inst. 
for radio. All boxed S/- 
per set. 



UNIJUNCTION 

UT46, Eqvt. 2N2646, 
Eqvt. TIS41. BEN3000 

7/6 EACH 
SIL. RECTS. TESTED 

PIV 750mA 3A IDA 30A 
50 2/- 1/- 4/6 9/6 
1/6 
4 '6 

4/9 
6,i- 
6/6 
tf 
*/- 
10/- 



100 2/3 
200 2/6 

300 31- 
400 1/6 
500 41- 
600 4/1 
800 4/9 
I 000 6/- 



6/- 15/- 
6/6 20/- 
8/- 11/- 
9/- 25/- 
9/6 10/- 
10/- 17/- 
15/- 40/- 
17/6 50/- 



SCR's 

LOWEST PRICE 
LARGEST RANGE 

PIV IAMP 7A I6A 30A 

25 _ 7/6 — 30/- 

50 7/6 8/6 10/6 15/- 

100 8/6 10/- 15/- 45/- 

200 12/6 15/- 20/- 55/- 

300 15/- 20/- 15/- — 

400 17/6 IS/- 15/- 80/- 

500 10/- 40/- 43/- 95/- 

600 — 40/- 50/- — - 



ORPI1, ORP60 8/6 each 



PRINTED CIRCUITS 

EX-COMPUTER 

Packed with semicon- 
ductors and components, 
8 boards give a guaran- 
teed 30 trans and 30 
diodes. Our price 

8 boards 10/-. Plus 
2/- P. Bl P. 



TRANSISTOR MANUAL by g.e 

INC 

L.A. S.CR's. 

G.T. SWITCHES, 

THEORY, RATINGS, 

EACH APPLICATIONS. 

P.P. 1/6 

S.C.R. MANUAL by g.e. 



CIRCUITS, APPLICATIONS 

CHARACTERISTICS, 

THEORY. 



647 PAGES 



30/- 



SILIGON PLANAR TRANS. 1/- 



2H706 

EACH KPN 



tlNG OF THE PAKS satisfaction guaranteed 
SUPER PAKS— BRAND NEW 
I (.tested Semiconductors 

PAK NO. 

Ul 120 Glass S.ub-m in. General Pur- 
pose Germanium. Diodes ... 10/- 

U2 60 Mixed Germanium Transistors 

AF/RF ...- 10/- 

U3 75 Germanium Gold Bonded 

Diodes Sub-min, Sim. OA5, OA47 10/- 

U4 40 Germanium Transistors like 

OC8I.ACI2B ... ... ... W- 

U5 60 200mA Sub-min. Sil. Diodes 10/- 

U6 40Siiicon Planar Transistors NPN 

Sim. BSY95A. 2N706 10/- 

U7 16 Silicon Rectifiers Top-Hit 

750mA VI tg. Range 0-1.000 ... 10/- 

U8 50 Silicon Planar Diodes DO-7 

Glass 250mA Sim. OA200/202... 10/- 

U9 20 Mixed Volts I watt Zener 

Diodes 10/- 

UIO 20 BAY50 charge storage Diodes 

DO-7 Glass 10/- 

Ul I 30 PNP Silicon Planar Transistors 

TO-5 Sim. 2NII32 10/- 

UI2 12 Silicon Rectifiers Epoxy 500- 

mA up to 800 PIV 10/- 

UI3 30 PNP-NPN Sil. Transistors 

OC200 and 2SI04 10/- 

UI4 150 Mixed Silicon and German- 
ium Diodes ... 10/- 

UI5 30 NPN Silicon Planar Tran- 
sistors TO-5 Sim. BFY50, 2N697 10/- 

UI6 10 3A Silicon Rectifiers Stud 

Type up to 1 ,000 PIV 10/- 

UI7 30 Germanium PNP AF Transis- 
tors TO-5 like ACY 17-12 ... 10/- 

U18 86A Silicon Rectifiers BYZI3 

Type up to 600 PIV 10/- 

UI9 30 Silicon NPN Transistors like 

BOOB 10/- 

U20 12 I-5A Silicon Rectifiers Top 

Hat up to 1,000 PIV 10/- 

U2I 30 AF, Germanium Alloy Tran- 
sistors 2G300 Series and OC7I 10/- 

U22 10 IA Glass Min. Silicon Recti- 
fiers Hieh Volts 10/- 

U23 30 MADT's like MAT series PNP 

Transistors ... ... ... 10/— 

U24 20 Germanium I A Rectifiers 

GJM Series up to 300 PIV ... 10/- 

U25 25 300Mc/s NPN Silicon Tran- 
sistors 2N708, BSY27 10/- 

U26 30 Fast Switching Silicon Diodes 

like IN9I4 Micro-Min 10/- 

U27 12 NPN Germanium AF Transis- 
tors TO-I like ACI27 10/- 

U28 Experimenters Assortment of 
Intregated Circuits, Untested. 
Consisting of Gates, Flip- Flops. 
Buffers, Registers, etc. In Fiat- 
Pack and Dual-in. Line, B Assor- 
ted Pieces ... ... 20/- 

Code Nos. mentioned above are given as 

a guide to the type of device in the Pale, 

The devices themselves are normally 

unmarked. 



INTEGRATED 
CIRCUITS 

Epoxy TOS 8 lead 
*jL 900 Buffer @ 11/- 
jiL 914 Dual Gate 

® H/- 
ItL 923 J-K Flip Flop 

% 14/- 
IC circuits data, 
etc. 1/6 



TAA263 21/- 



6 VHF trans, 667 eqvt. 
AFI 16-11/ 10/-. 



0CP7I 
8/6 each 



IMPORTANT NOTIf F VVE HAVE NOT CHANGED OUR NAME OR AMALGAMATED 
inrunifini nwuvc W|TH ANy OTHER PAK F|RM YOU CAN qnly OBTAIN 

OUR ADVERTISED STOCK BY SENDING TO: C.W.O. p/etweodd 1/- p. & p. Mln. Order 10/- 
BI-PAK SEMICONDUCTORS, 8 RADNOR HOUSE, 93-97 REGENT ST., LONDON, W.I 



30 FOR 107- 



BI-PAK GUARANTEE SATISFACTION OR MONEY BACK 



452 



RECEIVERS AND COMPONENTS (continued) 



TRANSISTORS EX STOCK 



WE ALSO STOCK: 



AC 1 07 


14 6 


AC 127 


61- 


AC 128 


41- 


AC 176 


61- 


ACYI7 


5/- 


ACY20 


1/6 


ACY2I 


4,- 


ACY22 


m 


AD MO 


12/B 


AD! 49 


11/- 


ADIfil 


7,.'6 


AD 162 


7/6 


ADTI40 


11/6 


AFI02 


IB/- 


AFI 14 


4/9 


AF! 15 


419 


AFI [6 


419 


AFI 17 


419 


AFI86 


12/- 


AF239 


II- 


AFZII 


10 - 


AFZI2 


119 


ASY26 


5/- 


ASY28 


5/- 


ASY29 


6/6 


ASZ2I 


41- 


BAIIS 


a/ft 


BC107 


4/J 


BCIOB 


4/- 


BCI09 


4/3 


BCY30 


71- 


BCY3I 


91- 


BCY32 


91- 


BCY33 


61- 


BCY34 


31- 


BCY38 


l»/- 


BCY40 


16/- 


BCZII 


10/- 


BFY50 


*/- 


BFY5I 


w- 


BFYS2 


61- 


BSX76 


lt- 


BTY7 9-400 R 


24/6 


BTYB7-I50R 


23/- 


BTY91-IS0R 


35/- 


BTY87-SO0R 


47/- 


BYZIO 


II;- 



BYZI2 
BYZI3 
BYI00 

BYX20-200 

BZY93 

GET 1 02 

GET 1 03 

GET1I1 

GET573 

OA5 

OAI0 

OA47 

OA70 

OA73 

OA79 

OA81 

OA65 

OA90 

OA9I 

OA9S 

OA200 

OA202 

OCI9 

OC20 

OC22 

OC23 

OCI4 

OC2S 

OC26 

OC28 

OC29 

OC3S 

OC36 

OC4I 

OC42 

OC43 

OC44 

OC45 

OC7I 

OC72 

OC73 

OC7S 

OC76 

OC8I 

OCBID 

OCB2 

OC82D 



7/6 OC83 


3/64 


5/- 


DC84 


4/-1 


51- 


OCI23 


7/-I 


•/- 


OCI39 


I1M 


12/- 


OCI40 


11/-I 


514 


OCI69 


•/- 


4/4 


OCI70 


41-1 


10/- 


OCI7I 


6/- 


10/- 


OC200 


6/- 


3/- 


OC20I 


10/- 


4/- 


OC202 


11/- 


1/6 


OC203 


31- 


l/« 


OC204 


11/- 


1/6 


OC205 


10/6 


1/6 


OCP7I 


19/6 


1/6 


ORPI2 


»/- 


1/6 


ORP60 


8/- 


1/6 


ORP63 


91- 


1/6 


ORP93 


18/- 


1/6 


ORP90 


19/6 


2f- 


MATIO0 


7/9 


2/- 


MATI0I 


1/6 


51- 


MATI20 


T/9 


33/- 


MATI2I 


8/6 


11/- 


STI40 


lf- 


23/- 


STI4I 


51- 


191- 


TAA262 


29/6 


7/- 


IB40KIO 


!»/- 


12/- 


2N1302 


51- 


12/- 


2MI303 


51- 


15/- 


2NI304 


61- 


9/6 


2NI305 


6/- 


13/- 


2NI306 


8/- 


3/6 


2N1307 


8/- 


4/- 


2NI308 


10/6 


3/- 


2NI309 


18/6 


8- 


2N2I47 


17/- 


n- 


2N2I60 


14/9 


i/- 


2N2646 


10/- 


4/6 


2N2926 


3f- 


3/- 


IN 3528 


19/- 


51- 


2N38I9 


11/- 


1/- 


2N3926 


6/- 


17- 


UL90O 


11/- 


V- 


UL9I4 


11/- 


4/6 


UL923 


14/- 


4/1 







BARGAINS IN 

SEMICONDUCTORS 

ALL TYPES 



COMPONENTS 

7 COPTFOLD ROAD 

BRENTWOOD ESSEX 

BRENTWOOD 7904 

24 HOUR POSTAL SERVICE 



GUARANTEE: All the above-listed semiconductor devices am Brand New, Fine 
Grade, and guaranteed. We will replace at no charge any device found to be faulty. 
Further: all devices carry the Manufacturer's name or Trade Mark, type number 
and batch number. We do not offer for sale devices often described as "new and 
tested" or bearing re -mar Iced type numbers, these often have a short and unreliable 
life. LST COMPONENTS 



20 watt Solid State Amplifier Kit— AFI I £8.8.0 

Solid State Pre- Amp for above, Complete £6.10 J 

Send now for details 

"S-Dec" Breadboards ■ *•/• 

i and i watt 5% Carbon Film Sub-Min. Resistor* 4d each 

Skeleton Presets - '/■ 

Mullard Sub-Min. Electrolytics and Polyester Capacitors 

Heat Sink Tor 2 X OC35, etc *'- 

Veroboard — All standard sizes 

Aluminium Chassis and Panels 

Internation Rectifier 

SEMICONDUCTOR CENTRE Stockist! 

MULLARD & FAIRCHILD Integrated Circuits 

Handbooks of all types 

40kc/s Transducers fj £5.18.0 pair with free circuits. 

"X"-Line Modules — Solid State — read* built and tested circuits 

ALL THE ABOVE AND MUCH MORE 
IN OUR 1968 CATALOGUE 

PLEASE SEND TO ME YOUR 14 RAGE CATALOGUE 

I enclose I ,'6 stamps 

NAME ■ 

ADDRESS 

BLOCK 'LETTERS PLEASE «/•' 



DECADE COUNTER UNITS. L'nliiii; ■:! l.C.sand 

silicon translators. Mnx.,p.r.f. above 2MHz, 
B.C.I), output, met-ttM, M MS o-7in, 
M, ; - each inr, postage, ft. MOUNT, Keld- 
holme, Linton, Votlwrby, Yorks. 



TRANSISTOR 
TROLYT1CJ 

SOOmfd 4V 
320mfd 10V 
250mfd 4V 
200mfd 16V 
lOOmfd 16V 



CAPACITORS {ELEC- 



64mfd 40V 16mfd 2SV 
50mfd 10V lOmfd 25V 
30mfd 10V 6 4mfd 64V 

ISmfd 25V 4mfd 64V 

20mrd 12V Imfd 2SV 

/- each. 9/- per doa. Min. order 10/- 
TRANSISTOR PANELS— OC45 or equiv., 
20 for 20/-, 30—25/-. 50—15/-. 70—45/-, 40— 
30/-, 60 — 40,'-, 80 — 50/- Postage 2/- per panel 
Brand net" STC sil. EPT planar transistor* 
300 Mets 350 mW, all at 2/- each. 2N743, 
2N753, 2N9I6. BSY26, BSY2B, BSY65, BSYI8, 
BSY9SA. BSY29 

TRANSISTORS OC45. TK21C S! I/- each. 
OC76. OCI39, IG302. OC81. OC44 g 1/- each. 
GET 1 20, OC83. 7NI308, OC72. NKT2I6 @ 
4/- each. OC23. NKT452. NKT453 6/- each 
10 watc heat sink drilled for power trans. 5/-- 
I.OOOmfd 30V Al~. 3,000mfd 10V 2/-. T.V. 
capacitors 100 + 200 + 400mfd 27SV 7/6. 
100 + lOOmfd 300V 5/6. 

W.W. POTS 5. 10, 25. 50. 100, 150, 500 ohms, 
Ik, 2k. 2-5k, 5k. 10k. 25k, 50k. 100k, not 
preset!/- each. Min, order 5/-, Pottage 1/- 
ZENER DIODES— 2-4. 2-7, 3 6, 4-75. S-25, 
5-75, 6-2, 6-8. 7-5, 9-1. 13, 15, 16, 18, 20, 27, 30, 
33 volts. 3/6 each, mostly I watt 
POLYSTYRENE CAPACITORS I50V: 180, 
270. 330. 390. 470. 560. 680, 820pC 1,800, 2,200, 
2,700, 3,100, 5,600, 6,800, 8,200 
125V: 1.200, 1,500. I ,B0O, 2.200, 2,700, 3.300, 
3.900, 4,700. 5.600, 6,800. 8,200. 00 1 2. 015, 
80pf ceramic 200pf S.M. any selection 2/- doi. 
4-40pf trimmers 4i- doi. 

BRAND NEW BOXED CHASSIS, contain- 
ing 2— OC3S, 2— OC29 12 WW resistors 30/-. 
Postage 1/6. 

STEREO POTS. Less switch, single spindle. 
I meg + I meg log and I meg log + I meg rev/ 
log. 7/6 each. 

NEW CROSS RADIO 

6 OLDHAM ROAD, MANCHESTER 4 



STUDENT ELECTRONIC SERVICES 
194 Regent Road, Sal ford 5 

We stock a wide range of Resistors | »nd 

i watt. 

Buy individually OR try the S.E.S. Pre-Pack. 

Stocks now include Potentiometers — Log. 

and Lin. 

Enclose 6d. for complete price list. 



RESISTORS 

£ watt carbon film 5% 

All preferred values in stock from 

10 ohms to 10 megohms 2d. each. 

Send S.A.E. for free sample 

CAPACITORS 

Milliard Miniature Metallised Poly- 
ester P.C. Mounting, all 250V D.C. 
working. 001 mf. 022mf. 047mf, 
0-lmf, 0-22mf, all at 6d, each 

Hunts tubular 0-1 mf 200V working 
at 3d. each 

Send 6d. stamp for extensive list of 

low priced Electronic Components, 

Instruments and Equipment 

Phase include ! /- postage and pocking 
on alt orders under £1 

Dept, P.E.12 
BRENSAL ELECTRONICS LIMITED 
CHARLES STREET, BRISTOL 1 



INTEGRATED AMPLIFIER 1«A H020 55flmW 
i-lass II ami), i" T()5 cnii. With data, 33/-. 
List iki. A MATROX IX LTD., :jl»« Splsdon 
Road, Croydon, Surrey, CMS (JDK, 

BRAND NEW ELECTROLYTIC!, Mil. -minia- 
ture 15 volt, S, 10, :«1, ill), loom l\ 16 per doz. 
post 1/-. The (Ul. SUPPLY CO., 127 Chester- 
field- Head, Sheffield, Srt OUN". 



COMPUTER PANELS 

Eight assorted printed 
circuit panels with tran- 
sistors, diodes, resistors. 
capacitors, etc. Guaran- 
teed minimum 30 
transistors. Ideal for 
Experimenters, 6 boards 
10/-. POST FREE. 
100 Boards 6SI- 
ROST FREE 
1 500+2009 MFD Electro- 
lytic! 25 volt DC wIce. 
3,'- each. 9d. P. & P. 

KEYTR0NICS, 52 Earls Court Road, 
London, W.8. Mail order only 




R & R RADIO 

51 Burnley Road, Rawtenstall 

Rossendalo, Lanes 
Tel.: Rossendalo 3152 

VALVES BOXED, TESTED & GUARANTEED 



EBF30 


Jf- 


PCC84 


1/- 


PYB2 


3/- 


EBF69 


3/6 


PCFB0 


1/- 


UI9I 


4/6 


ECCB2 


3/- 


PCF82 


3/6 


U30I 


4/6 


ECLBO 


3/- 


PCL62 


4/- 


6F23 


*/- 


EFS0 


1/6 


PCLB3 


41- 


I0PH 


3/- 


EF85 


3/- 


PCL84 


51- 


20P5 


3/- 


EFI83 


3/6 


PL36 


51- 


30F5 


2/6 


EFI84 


3/6 


PLBI 


41- 


30LI5 


5/- 


EY84 


4/- 


PL83 


4!- 


30PI2 


4/6 


EL4I 


5/- 


PY33 


31- 


30CIS 


31- 


EZ40 


4/6 


PYB1 


3/6 


30PL13 


S/6 


EBC4I 


4/6 


PY800 


3/6 


30PLI4 


9/6 



POST, ONE VALVE »d. TWO TO SIX 6d. 
OVER SIX POSTPAID. 



453 



RECEIVERS AND COMPONENTS (continued) 



STUDENT ELECTRO N I C SERVICES 

194 Regent Road, Sal ford 5 

Constructional aids — -including 
Assembly Stand (each individually 
made by craftsmen). 

LEKTROK1T — the biggest money and 
time saver sint'e the 
safety pin ! 

Everything to construct a pro- 
fessional job, from a variety of 
boards, pins to chassis plates and 
rubber feet. 

Special introductory kit in 2 sizes. 

Write now for complete price list 
AND sample resistors, enclosing 6d. 



SEMICONDUCTORS 

All Brand New Milliard or Newmarket, 

No Rejects, 

2N2926: Green 8 235 470. 3/9; Yellow 

& ISO 300. 3/6; Orange 90-180, 3/3; 

Red fl 55 I 10, 3/-. 

ACY22 3/- 2N706 3/- 

BCI07 5/- 2N708 4/6 

BCI0B 4/6 INI 132 12/6 

BCI09 S/- OC7I 3/- 

BFY50 7/6 OA70 1/6 

BFYSI S/6 OA8I 1/6 

BFY52 7/6 OA90 1/6 

BSY95A 4/6 OA9I 1/6 

2N697 6/- OA202 2/6 

Resistors, j watt earfoon, all preferred 

values 3d each. 

P. & P. I/-, free on orders over 15/-, C.W.O. 

Dept. P,E. W. W. Electronics 

10 The Drive, Newcastle on Tyne, 7 



TRANSISTORS 
1,000,000 FOR SALE 

BRITISH MANUFACTURERS 
SURPLUS 

Owing to the reorganisation and expansion 
by the manufacturers of these transistors, 
it has been necessary to clear them as 
surplus to requirements. These devices 
would normally be tested several times 
into different groups, 50 ",, would be used 
as good industrial transistors and a further 
35 " would make diodes. The remaining 
IS",, would be disposed of as scrap 
rejects. 

Offering these devices in varied quantities 
make them ideal for AMATEUR 
ELECTRONICS, RADIO HAMS and 
for EXPERIMENTAL USE IN 
SCHOOLS, COLLEGES and 

INDUSTRY. 

All transistors are in mixed lots, mainly 
PNP but some NPN, all are Germanium 
type. Prices and quantities as follows: 
approx. count by weight 
100 pieces . . . . . . 10/- 

300 „ *W- 

SOO „ . . . . . . 4°/- 

i,ooo „ . . - - • ■ 60/- 

10,000 „ . . - - . . £25 

Large quantities by negotiation. 
TERMS— CASH WITH ORDER, all 

goods sent by return. Please add 2/- 
towards Post & Packing orders up to £3, 
over £3, 5/-, Monthly accounts for Educa- 
tion Authorities, etc, on receipt of an 
Official Order. 

EXPORT ENQUIRIES WELCOME 

All correspondencCj cheques, Postal 
Orders, etc., to: 

DIOTRAN SALES, P.O. Box 5, 
63 High Street, WARE, HERTS. 
Tel.: WARE 3442 



CHASSIS, Brand new I Gin :< I I ;in, 18 gauge 
steel chassis with front panel, ready punched 
and stove enamelled silver hammer. Suitable 
for power supply, ecc, JO/- each. 4/6 P. & P. 

Brand new IQin *■: Sin, 16 gauge aluminium 
chassis, ready punched for two relays, tag 
strips, etc.. S/6 each. 2,'- P. & P. 

RELAYS. I. Heavy duty type, suitable for use 
in cars, etc., 30 ohm coil, two sets of contacts, 
supplied on mounting bracket containing 
dropper resistor and input socket. 15/- each. 
1 /« P. & P. 

2. 3000 type, brand new. six pairs of change- 
over contacts. 200 ohm or 1 ,000 ohm coil, 
t0/- each. I/- P. & P. 

3. 600 type, 1,000 ohm coil, one set of 
contacts, 4/- each. I/- P. & P. 

CONSTRUCTING YOUR OWN 

RELAYS? Brand new and boxed relay 
contacts. Two pairs of change-over contacts 
per set. 3,000 type, four sets 10/-; medium 
power type, four sets 7/6. I /- P. & P. 

UNISELECTORS, Unused but soiled due to 
warehouse storage. 8 bank, 25 position, 
75 ohm coil, 19/- each. 3/- P. & P. 4 bank 
(+ I shorting bank), 25 posn., 75 ohm coil, 
19/- each, 3/- P. & P. 3 bank, 25 position, 
12 ohm coil, 15/- each. 3/- P. & P, 

PHOTOTRANSISTORS. OCP7I equiva- 
lents, 5/- each. P. & P. 6d. 5 for £1 post free, 

AVO VALVE TESTERS. Two only. Cur- 
rently selling at £30, a bargain at £20 plus £1 
carriage. 

BUILDING YOUR OWN TAPE DECK? — 
TAPE REVERB UNIT? Professional quality 

7 Sin dia. rubber pinch rollers, with precision 
ground face and nylon bearing insert, suitable 
for any type of tape transport system, 2/- each, 
P. & P. 6d. Prices for larger quantities on 
application. 

POSTAL SERVICE ONLY— REGRET NO 
CALLERS. 

BEEJAY ELECTRONICS 

106 REDDICAP HEATH ROAD 
SUTTON COLDFIELD, WARKS. 



CURSONS 

TRANSISTORS 
ALL GUARANTEED 

1/- each 

BAY31, BAY50, DK10, OA70, 
A81 , A2Q0, O A10, A90, A91, 
OA259, IN914, IN916, JL102 

2/- each 

XA101, XA102, OC71, OC72, 
OC81, OC81D, OC44, OC45, 
GET16, FST3/1, ACY22, ASY57 

3/- each 

OC139, OC140, 2N706, 2N708, 
2N2894, BY100, RAS310AF, 2N914, 
BSY26, BSY27, BSY95A, AFZ12 

7/6 each 

RAS508AF, CRS3/40, BLY10, 
BLY11, BUY10, BUY11, ADY22, 
ADY23, ADY24, OC22, OC26 

ZENER DIODES 

3-9v to 26v, ^w 3/- each, 1-5w 4/-, 
7w 5/- each. 



B. 



CURSONS NEW LIST 



78 BROAD STREET 

CANTERBURY 

KENT 



REPANGO Transistor Colls and Transformer. 
for the Constructor. Send stamp for lists 
RADIO EXPERIMENTAL PRODUCTS 
LTD., 33 Much Park Street, Coventry. 



MICROMINIATURE MICROPHONES 

Sensitive dynamic type. Will pick* 
up rustle of newspaper from 30 feet, 
Siae 9 mm. X 9 mm. x 3*5 mm. 
Impedance I KQ, 

ONLY l*/ft 
Post free — C.vV.O. 

MICRO DATA SYSTEMS 
30 BAKER ST., LONDON, W.I 




PHOTO ELECTRIC CONTROL 

PUPTCU Comprises a light source unit with 
U I O I Lltl optional Infra Bed alter and lens 
system to force the light. Also a 
photo-electric Relay control unit. Both boused in 
niclnl cases for bench or wall mounting, sensitivity 
control, mains on*off switch. Works from 230/240 V 
a.c. Mains. Can be used as a simple on-oft switch by 
breaking the beam ol light (Invisible if Infra lied 
filter Is usi?'.1) ami as such it will operate as a burglar 
alai ut, or will open ilnora, ete. Also In conjunction 
with a counter or other, equipment it will perform 
many functions iu the factory or fO IO A 
warehouse. fcF» I T*V 

F.M, WIRELESS MICROPHONE 
94-104Mg/s. Transistorised, Operates from 0V 
battery. Complete with additional secret tie clip 
microphone. List £12/10/- OXLY XjL I C Q 

These cannot be operated in U.K. fc»*» ■ *#•*» 

TBAKBISTOBISED FM TuTfEK 
B TRAysiSTOB HIOH QUALITY TL'NKB. 
S1ZK ONLY flfn 4 in >: 2Jin 3 I.E. stages, Double 
tuned discriminator. Ample output to feed most 
amplifiers. Operates on DV batten-. Coverage 
0O'iOSMc/e. Heady built ready for £_(. I J i 
use. F antastic value lor money L " ' ' 

PM MULTIPLEX STEREO ADAPTOR 

Printed circuit biscuit, 4 trans, fi £C 10 A 

tlimles SiV with lull instructions ».J< i #•« 



BSR TAPE HEADS 
BRAD, 

2 TRACK 



39/6 



BSR TAPE MEADS 

HALL 7Q f. 

4 TRACK JT/Opair 



KEFLEX CONE TYPE 
WATERPROOF SPKE. 
;. <m -ut, 3 ohm. 300- 
lu.OOOeis PA (A c n 
& Music Betas " ,J,W 



MULTDMETEE8 Xli- 
Irom ""*/ 



LOUDSPEAKERS. :TQ/C 
40 ohm, 21' 30 ohm, 0/U 
12-TWIHCONE3U ncj 
watt. 15 or 3 ohm <W - 
TWEETER 16 u hi 1 1 nn/O 
10 watt, 18K-CF3 63/ U 
CROSSOVER SB 
WORK 16 ohm 



SUPER SILICON RECT. T.V., etc., 1,200 FIV 

800mA, 6'-; or complete with instf. resistor, 
coiidenser.7/6; 400 P1V HW B.\, 6/-; 200riVKW 
BA. St-. 

Stamped envelope for full selection ami bargain 
offers in Multimeters, Railio*, Baby Alarms, Inter- 
coms, W'alkiH-T.ilki.'S, Recllliers ami Eagle Lists. 
i;NWEK £1 I>, & r. M. OVER £1 post free. 
C.O.O. a/6. 

DURHAM SUPPLIES 
175F. Durham Road, Bradford. 8, Yorkshire 



ELECTRICAL 



DRILL 

EXTENSION 

LEADS 




20' 18/9 
30 24/9 



Best quality 3 core cable used. Fitted with 
unbreakable rubber plug and socket in either 
13 amp., 5 or 15 (state choien). Will aiso extend 
/our vacuum lead, hedge trimmer, mower, etc. 

SOUTH WEST SUPPLIES {Dept. PI) 
222 Fishponds Road, Bristol S 



DON'T MISS THIS OFFER 



British Made Electric Soldering Iron, 6 month* 
Makers Guarantee AND After Sates Service. 
30 watts 230-7.50 voles or 200-220 volts, state 
choice,, supplied with over I Oft. of 3-core pvc 
flex. This is a quality iron at the ridiculous low 
price of ONLY 16/- + 1/6 P.P. SOUTH WEST 
SUPPLIES, 222 Fishponds Road, Bristol 5. 



454 



COMM/CAT/M 



TYPEGDX 




The Latest version of the T.R.GDX Series. 
The type 25/C improved model. A 
brand new fully transistorised receiver. 
Four complete ranges 550kc/s to 30mc/s 
covering all amateur bands, shipping 
bands and broadcast bands. Tt is a highly 
efficient double tuned superhet comprising 
R/F aerial tuning section, AVC and buih 
in B.F.O. (tunable) for C.W. or S.S.B. 
reception. Ideal for mobile reception. 
Size only 9 X 7 X 6in. Operates from 
internal 9 volt battery. Gives a high quality 
reproduction. With speaker or headphone 
output. Hammer finished robust steel 
case of pleasing design, with all controls 
on well set out front panel. The set 
complete with handbook, 14 gns. Car- 
riage 16/-. Headphones, 19/6 extra; 
P. & P. 3/6. ACCESSORIES: fitted S 
meter £2 extra. Stabilised miniature 
battery eliminator, 50/- P. & P. 5/-. 
De-luxe loudspeaker in matching metal 
cabinet £2.15.0: carriage 5/-. 





comoLbut 



MK V. 3,000 WATT MODEL, Finger tip 
control of all a.c./d.c, electrical equipment. 
Suitable for all types of lighting arrange- 
ments. Incandescent lamps, spot lamps, 
arc lamps. Floodlights, Makes an ex- 
cellent dimming unit. Ideal for controlling 
all types of electric heaters. Electric 
blankets and electric irons. Will control 
the speed of all drills for all applications. 
Also lathes and power tools. Contains 
the latest electronic switching devices, and 
associated Thyristor circuitry. Size 
6x5 :; 2in. Louvercd metal case in 
pleasing hammer finish. Attractive front 
panel with matching socket and control. 
Ample cable provided. Additional cable 
3/6 per yard. The recommended price of 
the unit is 25 gns. Due to another bulk 
purchase we can offer them at only 
£8.10,0. carriage and insurance 10/-. 
C.O.D. 3/6 extra. 

TWO WAV TALKIE PHONES. Ideal for 

indoor/outdoor Communication. Will work 
up to long distances. Clear reception. No 
G.P.O. licence required. Once complete set 
£2.10.0: carriage 10/-. Batteries 10/- extra. 
Special offer of Two complete sets plus 
batteries £6 post paid. 

All orders to: Dopt. P.E.U 

^riiii:iMHM;nni8mH 

It CAWOODS YARD, MILL STREET 
MARSH LANE, LEEDS 9 (LEEDS 35900) 

Callers welcome. Open 7 days a week 

New Component Centre opening 20ch May 

at this address. 



CRESCENT RADIO LTD. 

(electronic component specialists) 

For oil regulor component* try 
40 Mays* Road, Wood Green, N.ll 
For surplus components and erru/brnent try 
II Mayes Road, Wood Green, N.ll 
BARGAIN BOARD 
7in X Sin board with the following compo- 
nents attached : 

2 GET872A transistors 
2 Milliard OAI0 diodes 
2 Mullard OAS diodes 
12 Midget iW Resistors various values 
B Midget Capacitors various values 
including postage in Great Britain 4/- each 

BARGAIN CHASSIS 
All usable components 
I Electrolytic capacitor I0O plus lOOrv.F 
I Electrolytic capacitor IQOmF « 150V 
I Electrolytic capacitor 8mF " 450V 

1 OI2mF ■'. 600 V 

2 Silicon Diodes 

2 Preset Pots (I) SOOkfl. (I) 2Mii, 
t 2m F 350V 
5 mixed resistors 

I Transformer 8'6 each 
SPECIAL LINES 
Airspaced capacitor 50pF with 

standard spindle 2/6 each 

B ohm transistor earpieces I 6 each 

Heavy duty 1-25 ohm slidei reiistor 9d each 

Double pole knife switches 1/6 each 

G.P.O. 1,000 ohm relays 5/- each 

500 ohm midget relays, 9V 5,'- each 

45 m/h Ferroxcjbe choke, L.A.3 size. 4,'6 each 

00 gangs 208/ 1 76pF 4/6 each 
5kO midget transistor pot with S.P, 

switch 2/6 each 
Twin transistor cooling clips OC8I 

size 6d each 
Black and satin chrome liin. knobs, 

standard spindle 1/3 each 

IkO Bercostac pot 4/6 each 

B.S.R. erase heads 5/- each 
Mains indicators, yellow and green. 

fin fixing !.'» each 

VERO BOARD 

3f X 3iin 015 pitch 2,'- each 

TRANSISTORS 

2G339A 1.6 each 

Matched pair 2G378B and 2G339B 3 '6 each 

2G40I 2/6 each 

2N7I I 2/6 each 
With our new premises in Mayes Road we can 

now offer an even wider selection of com- 
ponents for the home constructor and 
enthusiast. 

POSTAGE WITH ORDER PLEASE 



AEEIAL WIRE; Coils at 25 vd. Single Strand 2/84 

fid P. * P. 

BELAYS' 

1. Miniature Plug-in Relays. 1S6 Coll 4.6/18V. 
3 Change over Contacts 18/84- 1/6 P. * P. 

2. Miniature Plug-In Relays. ISO Coil 4, Light Duty 
Contact*. 9/ 16V. 1B/9 + 1/G P. & P. 

3. 6V octal base A/C Relays, 2 pairs heavy duty 
contacts c/o. Complete with octal base. 28/- 4 
1/8 P. A P. 

4. Single change over Relay. B76 Coll. 18V lor 
printed circuit. 16/-41/6 P. * P, 

6, Bases lor Item 1 and 2. 3/9 40d P. & P. 

State whether wired or printed circuit. 

TEST KETER : 20 K per volt ITI-2. t3,9.8. 

PT31 small test meter II. 14, 043 1- P. * P. 

TAYLOR Jvm. 110,10.0. AVO Minor 89.10.0, and 

many others, 

LOUDSPEAKERS: 8 OEM 2" to S' from 7/8 to 18/6 

4-1/6 P.* P. 

Cat Speakers V X *' 18/842/- P. 4 P. 

TRAITSFORMERS : 250-0-250 sec. 60 M/A'ti -3V. 

18/943/6 P. 4 P. 

250-0-250 sec. 100 M/A/63V. 89/6+3/8 P. & P. 

TRANSFORMERS SUITABLE FOR SHALL POWER 

SUPPLIES; 0: 11/17 V at 4 amps. 87/843/0 P. & 

P. 3 to 30V tapped 2 amps. 80 '-4 3/8 P. 4 P. 

0-9-15V. li amps. 18/843/- P. Je P. 7o\V auto 

transformers. 10/642/6 P. ft P. 

OUTPUT TRANSFORMERS : Suitable lor EL85 TLS4 

Singles. 6/642/6 P. * P. Midget Choke Output. 6/6 

42/8 P. & P, 

CONDENSERS ELECTROLYTIC : 2, 4, 10, 16, 30, SO, 

100 m.s.d. 15V. 1/8 44d. P, * P. each. 

CARBON CONTROLS: 5 K to 2 M Lin. or Log. 3;B 

41/- P. & P. 6 K to 2 M Lin. or Log. with »/\V. 6/8 

41/- P. & 1'. 

EAR PIECES: 2 5 mm or 3-5 mm Magnetic S/6. 

Crystal 2-5 mm, 35 mm. S/8, 

SINCLAIR PRODUCTS; All mill* and MM. Tim is. 

TRANSISTORS: Popular Range OVU, OC46, OCT J, 

OC72, OCai, OCS2, all at 2/6. 

POWER TRANSISTORS: OCW, 10,9. OCS8 16/8, 

OC35, 13/8, ADT149, 18/-. 

0SM0R RANGE ol IFs, Colls. Driver k output trans. 

ELECTRONIC KITS: Suitable lor beginners (2.17.8. 



"Write or call lor our free Components lint. 




BOTHWELL ELECTRIC 
SUPPLIES iQlaiKowi LTD. 
54 EGLINTON STREET, 
GLASGOW. C.6. Tel. 041 SOUlh 2904, 

Member ol the Lender Group 



TRANSISTOR 
BOOSTER 

39% 




100 



4UST PUCE 
HUH BADI0 




TO YOUR 
USTEMMa- 



The Dewtron Wave Trap lor portables 
•k Boosts Radio 1. Luxembourg, Pops I 
+ Eliminate* 'lading' 
■jt Extends battery lite, 
•jt Replaces car aerial lor portable eels. 
•fc 7-day return! trial, IS pnst lree. 
D.E.W. LTD..P.K 



The revolutionary \.U. Effects Amplifier adds 

Is labuloue "Big Hall Stereo" effect to any transistor, 

radio, tape or player. Adjustable echo, vibrato and 

tone. Requires only speaker and PP9 battery 

8 gas. + 4/- P. * P. Tubular speaker 25/- extra, 

CAR VERSION 10 Ens. with Mat ipetkat. 

HLNQWOOD ROAD. FESNDOWN, DORSET. 















BAR 3087 






WENTWORTH RADIO 












104 SALISBURY ROAD, HIGH BARNET 








ACY18 
ACY19 
ACY20 
ACY21 
ACY22 
ACY23 


4/8 
4/6 
4/3 
8/- 
3/8 
8/9 


BC100 5/- NKT217 7/9 NKT012 
BCY31 10/8 NKT2GI 3/8 XKT67& 
BFYoO W. NKT271 3/8 KKTBT8 
BWYBSA 67- NKT2TH 3.8 NKT71S 


4/11 
4/2 
4/2 
4,3 


OC45 
QG70 
OC71 
OC72 


i i 

6 
l'i 

IK 


OC170 

OC171 

I OC172 

20371 
2N404 

2N69I5 


2,8 
8/8 
4,'B 
8/3 

8/- 

*/e 










ACY32 
ACY40 
AD140 

AF114 
AF115 
AF116 
AF117 
AF118 
BC10T 
BC108 


5/fl 
3/10 
8/6 
4/3 

m 

E/3 

2/3 
4/8 
4/fl 
4/8 


BCY32 and BFY50 


7/- 


each 




2N706A 

2NI302 

2N1304 

StKISM 

2N1307 

2N13fl1 

2350 1 

I 2961 8 

I 2S746A 

I 293010 


4/8 
3/B 
4/8 
4/8 

71- 
t/- 
9/8 
4/8 
3/8 
8/7 


WATlOfl 7/9 NKT274 3/6 NKT773 
VIAT101 8/8 XKT304 11/- OC35 
SKTl 4/11 NKT403 15/- QC3U 
\KT214 3/8 XKT401 12.'- Of 44 


4'- 

8/8 
8 3 
I'll 


Ot'74 
OCTf. 
OC77 

DCS! 

Ol'llli 


3j 

m 

3.f 
If 

2; 






CASH WITH ORDER 


P 


. & P. N 


■ 







455 




PRINTED CIRCUIT KIT 

BUILD 40 INTERESTING PROJECTS on a PRINTED CIRCUIT 
CHASSIS with PARTS and TRANSISTORS from your SPARES BOX 

CONTENTS: < 1} 2 Copper Laminate Boards 4f :•: 2|'. (2) I Board for Hatch- 
box Radio. (3) I Board for Wriscwacch Radio, etc. (4) Resist. (5) Resist 
Solvent, (6) Etchant. (7) Cleanser/Degreaser. (8) 16-page Booklet Printed 
Circuits for Amateurs. (9) 2 Miniature Radio Dials SW/MW/LW. Also free 
with each kit. (10) Essential Design Data, Circuits, Chassis Plans, etc. for 

40 TRANSISTORISED PROJECTS 

A very comprehensive selection of circuits to suit everyone's requirements 
and constructional ability. Many recently developed very efficient designs 
published for the first time, including 10 new circuits. 

EXPERIMENTER'S 
PRINTED CIRCUIT KIT 

8/6 

Postage & Pack. 1/6 (UK) 

Commonwealth : 

SURFACE MAIL 2/- 

AIR MAIL 8/- 

Australia, New Zealand, 

South Africa, Canada 

(I) Crystal Set with biased Detector, (2) Crystal Set with voitage-quadrupler 
detector. (3) Crystal Sec with Dynamic Loudspeaker. <4) Crystal Tuner with 
Audio Amplifier, (5) Carrier Power Conversion Receiver. (6) Split-Load 
Neutralised Double Reflex, (7J Matchbox or Photocell Radio. (8) "TRI- 
FLEXON" Triple Reflex with self-adjusting regeneration (Patent Pending). 

(9) Solar Battery Loudspeaker Radio. The smallest 3 designs yet offered to 
the Home Constructor anywhere in theWorld. 3 Subminiature Radio Receivers 
based on the "Trifiexan" circuit. Let us know if you know of a smaller 
design published anywhere. (10) Postage Stamp Radio. Size only 1-62" x -95" 

x -25*. (II) Wristwatch Radio I IS" X 'SO" x 55'. (12) Ring Radio 70* >■ 
•70* X SS". (13) Bacteria-powered Radio. Runs on sugar or bread. (14) Radio 
Control Tone Receiver. (IS) Transistor P/P Amplifier. ( 16) Intercom. (17) 
l-valve Amplifier, (16) Reliable Burglar Alarm. (19) Light-Seeking Animal, 
Guided Missile. (20) Perpetual Motion Machine. (21) Metal Detector. (22> 
Transistor Tester. (23) Human Body Radiation Detector. (24) Man/Woman 
Discriminator. (25) Signal Injector, (26) Pocket Transceiver (Licence required). 
(27) Constant Volume Intercom. (28) Remote Control of Models by Induction. 
(29) Inductive-Loop Transmitter. (30) Pocket Triple Reflex Radio. (31) Wrist- 
watch Transmitter/Wire-less Microphone. (32) Wire-less Door Bell. <33) 
Ultrasonic Switch/Alarm. (34) Stereo Preamplifier, (35) Quality Stereo Push- 
Pull Amplifier. (36) Light-Beam Telephone "Photophone". (37) Light-Beam 
Transmitter. (38) Silent TV Sound Adaptor. (39) Ultrasonic Transmitter. 
(40)Thyristor Drill Speed Controller. 

PHOTOELECTRIC KIT 

CONTENTS: 2 P.C. Chassis Boards, Chemicals, Etching Manual, Cadmium 
Sulphide Photocell, Latching Relay, 2 Transistors, Condenser, Resistors, 
Gain Control, Terminal Block, Elegant Case, Screws, etc. In fact everything 
you need to build a Steady-Light Photo-Switeh/Counter/Burglar Alarm, etc. 
(Project No. I) which can be modified for modulated. light operation. 

PHOTOELECTRIC KIT 

39/6 

Postage & Pack. 2/6 (UK) 

Commonwealth: 

SURFACE MAIL 3/6 

AIR MAIL £1.0.0 

Australia, New Zealand, 

S. Africa, Canada & U.S.A. 

Also Essential Data Circuits 

and Plans for Building 

12 PHOTOELECTRIC PROJECTS. (I) Steady-Light Photo-Switch / Alarm, (2) 
Modulated-Light Alarm. (3) Long-Range Stray-light Alarm, (4) Relay-Less 
Alarm. (5) Warbling-Tone Alarm. (6) Closed-Loop Alarm. (7) Projector Lamp 
Stabiliser. (B) Electronic Projector Modulator. (9) Mains Power Supply. 

(10) Car Parking Lamp Switch. (H) Automatic Headlamp Dipper. (12) Super- 
Sensitive Alarm. 

INVISIBLE BEAM OPTICAL KIT 

Everything needed (except plywood) for building: I, Invisible-Seam Projector 
and I Photocell Receiver (as illustrated). Suitable for all Photoelectric Burglar 
Alarms, Counters, Door Openers, etc. 

CONTENTS: 2 lenses, 2 mirrors, 2 45-degree wooden blocks, Infra-red filter, 
projector lamp holder, building plans, performance data, etc. Price 19/6, 
Postage and Pack. 1/6 (UK). Commonwealth: Surface Mail 2/-; Air Mail 8/-. 

JUNIOR PHOTOELECTRIC KIT 

Versatile Invisible-beam, Relay-less, Steady-light Photo-Switch, Burglar 
Alarm, Door Opener, Counter, etc., for the Experimenter. 

CONTENTS: Infra-Red Sensitive Phototransistor, 3 Transistors, Chassis, 
Plastic Case, Resistors, Screws, etc.. Full Siie Plans, Instructions, Data 
Sheet "10 Advanced Photoelectric Designs", 
Price 19/6. Postage and Pack. 1/6 (UK). Commonwealth 2/-; Air Mail 4/-. 

JUNIOR OPTICAL KIT 

CONTENTS; 2 Lenses, Infra-red Filter, Lampholder. Bracket, Plans, etc. 
Everything (except plywood) to build I miniature invisible beam projector 
and photocell receiver. Price 106, Postage and Pack. I, <6 (UK). Common- 
wealth: Surface Mail 2/-: Air Mail 4,'-. 

YORK ELECTRICS, 333 York Road, London, S.W.1 1 

Send a S.A.E. for full details, a brief description and Photographs of ell Kits end 
all 52 Hadie, Electronic and Photoelectric Projects Assembled. 




R.S.T. VALVE MAIL ORDER CO. 

144 WELLFIELD ROAD, STREATHAM, S.W.16 

Special 24 Hour Mall Order Service 



A61 
AZ3I 

cic : 

CY80 ] 
IMF&i 

DAFae 

DCO90 

DF91 

DF96 

DH3/91 I 

DH77 

DK91 

DK92 

DK96 

DL66 

DL92 

DL94 

DL96 

DLS10 I 

LLS1S I 

DLS19 I 

DW4360 

DY86 

DY87 

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BI80F J 

E162CC ; 

EABC89 

EAF42 1 

EB91 

EBCS3 

EBC41 

EBC90 

EBF80 

EBFS3 

EBF89 

EBL2I I 

EBL31 : 

BOC33 ] 

ECC40 

BCCS1 

E0C8S 

ECC83 

ECCS3 

ECCSS 

BCFfjO 

KCFB2 

H:I3.i I 

ECH42 1 

ECH81 

ECHS3 

ECL80 

ECL82 

ECL83 1 

ECL86 

ECLL80U I 

EFS ' 

EF37A 

EF39 

EF41 I 

KF80 

SF86 

EF89 

EF9] 

BF92 

EF9B 1 

EF18S 

BF184 

EF604 S 

EFPflO 1 

EH 90 

EL33 ] 

EL34 1 

EL41 ] 

EL42 1 

KI.SI 

EL84 

ELB5 

EL86 



EX90 

ELB5 

EL360 

ELSOO 

ELS 31 
ELS22 

mhiso 

EM34 

EM80 
EMS ! 
EM84 
EN32 
EYfll 
EY81 
EY83 
EY84 
EY86 
EZ40 
EZ41 
BZ80 
BZ81 
GT1C 
GZ30 
GZ32 
GZ34 
GZ37 
BBS 



9/6 

22/- 

20/6 

8/- 

18/- 
20/- 
20;- 
7/6 
7/0 

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7:6 
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HL41DD 13/6 

KT61 12/6 

KT66 16/- 

KT67 46/- 

B KT81(7C6t 

8 15/- 

- KTSHGEO 

35/- 

KT88 27/6 

KTW61 10/- 

KTW62 10/- 

Mlrt 17/6 



-•:; 7 



17/6 
15/- 
11/8 
11/6 
8/9 
9/6 
6/3 
11/ 



N78 
FC86 
PCS8 
FC97 
PC900 
FCC84 
PCC89 

PCXJ189 11/6 
PCF80 7/- 
PCF86 9/- 
FCF801 10/- 
PCF802 10/- 
PCF8O6 13/6 
PCL82 7/9 
PC183 9/3 
rctai 7/9 
PCLSfl 9/3 
PCL86 9/- 
PENB4 20/- 
PEN4SD1> 

12/- 
PFL200 14/- 
|PL36 10/- 
FL81 8/- 

FLS2 
PL84 
FL500 
FX4 



l'X2ii 

PY32 

PY33 

PY81 

PY82 

PY83 

PY800 

PY801 

PZ30 

QQV02/6 40/- 



7/3 
6/9 
15/- 
14/- 
12/fi 
9/6 
9/6 
6/6 
ti.'- 
BH 
Hi - 
10/- 

111;'- 



QQV03/10 

30/ 
Q(iV03/20 

I Mi - 
QQV'04/15 

100/ 
QQV09/40 

£5.6.0 
QQV5/10 

70/ 
QS70/20 
Q 875/ 20 
Q 875/60 



20/- 
7/3 

ti- 
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QB83/3 
(J892/10 
QB95/10 
Q3108/45 15/ - 
(18150/15 8/- 
QS 150/30 5,'- 
Q8150/36 

20/- 
QS 150/46 

20/- 
QS 150/80 

20/6 
Q3 1209 7/3 
QV03-12 10/- 
QV04-7 12/8 
QV05-25 71- 
QV06-20 25/- 
R10 16/- 

K17 8/- 

B18 7/6 

Rie 

EQO/600 80/- 
8130 36/- 

8 13 OP 36/- 
SP41 3/6 

3P61 3/6 

3TV280/40 

26/- 6B37 
8TV2BO/80 6BW8 

85/- SBW- 
SU2160 12/6 
St2150A 12/6 



Z803U 

OA2 

OB2 

OC3 

OZ4 

1B3UT 

IRS 

2.D21 

2E26 

3A5 

3B2S 

3C4S 

4X150A 

5R4GY 

5U40 

SV4G 

6Y3GT 

6Z4(i 

6/30L2 

6AK6 

6AK6 

SALS 

6AM6 

SANS 

6AQ4 

6AQ6 

SABS 

SAS7 

6AT6 

6AU6 

SB4G 

6BA6 

6BE6 

BBHB 

6BJ6 

6BK4 

83X0 

6BQ7A 

SBR7 

6BE8 



16/- 
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4/8 

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5/- 

20/- 
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U19 
U24 
C25 

C26 
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U361 
U404 

U801 



35/0 
24/- 
13/6 
13/6 
13/6 
16/3 
11/9 
23/6 



L'ABCSO 8/- 

"" 10/3 

8 I 



UAF42 
CBC41 
UBC81 

LrBFSO 

UBF89 

UCC8S 

UCH21 

UCH42 

UCH81 

UCL82 

UCL83 

UF41 

UF89 

1JL41 

UL84 

UY41 

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SJ5G 
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6K8I; 
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10/- 68N70T 



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27/8 
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5/6 

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2/9 
5/- 
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13/- 811 



11E3 

12AC6 

1SAD6 

12AE6 

12AT6 

12AT7 

12AU7 

12AX7 

12BAB 

12BE6 

12E1 

12K7GT 

12K8GT 

12Q7GT 

20L1 

20F4 

20P6 

26Z4 

2SZ5GT 

26Z6GT 

30C15 

30C17 

30C18 

30F6 

30FL1 

30FL12 

30FL14 

301.1 6 

30L17 

30P12 

30F19 

30PU 

30FL13 

SOP 1,14 

35L6QT 

35W4 

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86A1 

86A2 

90AC 

90AV 

90C1 

90CC( 

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1WB2 

150B3 

801 

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813 
866A 



2/6'872A 
3/- 5651 
4/9 6664 

1; - iu72 



8/8 

25/- 
VR105/30 6/- 
VR160/30 5/- 
W81 6/- 

Z66 15/- 

ZS19 26/- 

Z759 23/- 



6V8G 

0X1 

6X50 

6X5GT 

7B6 

7B7 

7C5 

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5687 
5891 
5749 
5763 
5842 
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7/3 

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12/- 

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35/- 

71- 

30/- 

76/- 

13/6 

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7/8 

81- 

7/ 

10/- 

25/- 

10/ 

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ID/- 

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12/- 
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9003 9/ 

BY100 6/6 

TRAMSiSTORS 

1B131 4/S 



3152 

2G210 

2G381 

2G382 

SG401 

2G402 

2G414 

2G415 

2G416 

2G417 

2N217 

2N655 

AC107 

AC127 

AC128 

ACY19 

ACY20 

ACY21 

AS140 

API 14 

AFllo 

AF116 

GET571 5/- 

GET875 6/- 

t«KT211 6/- 

KK.T214 4/- 

NKT216 7/6 

KKT217 8/- 

NKT218 6/- 

NKT228 6/- 

NKT404 13/6 

NKT876 6/- 

NKT677 61- 

NKT713 7/6 

OC16 20/- 



4/3 

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OC24 
OC26 
OG26 

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OC29 

OC35 

OC44 

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OC71 

OC72 

OC74 

OC75 

OC76 

OC77 

OC78 

OC81 

OC81U 

0C81M 

OC81DM 8/- 

0C82 6/- 

OC82D 

0€83 



17/6 
16/- 
Of- 
11/- 
7/6 
18/ 
15/- 
11/6 
4/6 
4/- 
4/6 
6/- 
6/- 

$h 
» 

» 

a- 
4/- 
5/6 



0C169 
OC170 
OC171 
OC200 
SX642 
XA101 
XA111 
XA112 
XA125 
XA141 
XA142 
XA143 



TUBES 

1CT31 80/- 



Atl valves brand new and boxed. Postage 64. valve. 
OPEN DAILY TO CALLERS 9 a.m.— 5.45 p.m. No early closing 
C.W.O. Tel. 01-76? 0199 ft 1649 No C.O.D. 



SEND S.A.E. FOR LIST OF 2,000 TYPES. 




BAKER MAJOR £8 



The remarkable quality and performance 
of the "Major" makes possible truly 
brilliant and rich sound from a single 
loudspeaker. It recreates the entire 
musical spectrum from 40 to 14,500 c.p.i. 
The unit consists of the latest double 
cone, woofer and tweeter cone together 
with a special Baker magnet assembly 
Alcomax II having a flux density of 
14,000 causs and a total flux of 145,000 
Maxwells, Bass resonance 45 c.p.s. 
Rated 20 watts. Voice coils available 3 
or 8 or 15 oh mi. Price it, or Module 
version aa illustrated with tweeter, 
crossover and baffle, £10, 88*6* 



Baker Reproducers Ltd 



Bemham Manor Road Passage, Thornton Heath, Surrey. 01-684 Id65 



48 pace Enclosure 
Manual 5/9 Post Paid. 



456 



VALUABLE NEW HANDBOOK 

TO AMBITIOUS 





Have you had your copy of " Engineering Opportunities " ? 



The new edition of "ENGINEERING OPPOR- 
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On 'SATISFACTION OR 
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WHICH OF THESE IS 
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ELECTRONIC ENG. 
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THIS BOOK TELLS YOU 

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■jr HOW you can take advantage of the 

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132 PAGES OF EXPERT 
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Basic Practical and Theore- 

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NOW offers you a 
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SOLID HIGH FIDELITY AUDIO EQUIPMENT British made 

POWER AMPLIFIERS — PRE-AMPLIFIERS/CONTROL UNITS — POWER SUPPLIES 



-v ? 



— r • i i 



4 MPS 



tfSlTIITFilO *•» 



l # *«« •«: 



^ SP4-A 
SP6-2 



grte ft i « §* 



IS PAGE BROCHURE ON REQUEST. No 21 
All units sold separately, 



MPS mono preamplifier; 
control unit. £8,1 9,5 ^ a/ _ 

SP4-A niuuu/aterfsii vithioh of 
Mp 3 £11,19,6 pp . 4,6 

SPfl-2 mrinn /stereo (takes mag. 
pick* tap an well) 

£15.1u.Qp.p. 5 ,- 

MFA12/3 1-2 watt amplifier 
3 — 5 ohm output 

£4 1D.0 p. p .a/6 

MFAIS/IS 12 - 16 ohm 

12 mm £5.5. D p p 2/B 

MPAB5 "25-30 watt amplltter for 
7^-16 ohm speaker 

£7.10.0 p , r , m 

PS24/40 power supply for 
MPA12/:liMPA12,'15 

£3.12.6 p.p. s/- 

MU24/40 choke version 

£4.10.0 p-p 3 ' a 

MU80 pnvrer supply for 
MFA2S £4.17.6 pp- 4lfl 



AH systems complete with grey silver panels and matching silver 
knobB. 

Audio Equipment developed Irora Dinsdale Mi. TJ — each unit or 
system will compare favourably with other professional equipment 
selling at much higher prices. Brief details are below: 



Complete Aitgqtnitd if/Hems Frit? 


1A 

2A 
4 


MF3-MPAl'.!/3+MC24 


£ IS, 5.0 p.p. S/- 


MP3 + MPA12/15 + M.1'40 


£16.0.0 p.p. fi/- 


MP3 + C2) MPA12/15-HMU40 


£21.8.8 p.p. 7/- 


6 


MF3 + MP A25 + MU60 


£18.16.0 p.p. 71- 


8A 


SP4-A + <2) MPA12/15 + MU40 


£86.0.0 p.p. 8/6 


10 
ISA 


SP6-2 + ( 2) MP A 12/ 1 o + M V 4 


42S.S.0 p.p. 8/8 


SF4-A + {2) MPA25 + (21 MU60 


£35.10.0 p.p. 10/- 


13 


3P6-2 - vi > M P A-3-J - ! ••} M i ' lift 


£38.17.6 P.P. 10/- 



THE FINEST VALUE IN HIGH FIDELITY-CHOOSE A 
SYSTEM TO SUIT YOUR NEEDS AND SAVE POUNDS 



• COMPLETE RANGE OF SUITABLE PLAYER DECKS, SPEAKERS AND TUNERS IN STOCK.— ASK FOR LATEST LIST 16 • 



NEW! 




INTEGRATED 7 WATT AMPLIFIER 
AND PREAMPLIFIER — MA 7 

Sew design for 3 to 10 ohm speakers. Input 
for mag. ical ceramic pa's. Tape, tuner 
mic, etc. Batter; operated or mains unit 
Full Treble/Bass controls. 8 transistor 
design. 

PRICE £8.10.0 PJ. */- 

Leaflet on request (Mains in I PS 20 82/6. P.P. 3/-) 



TRANSISTOR 

P.M. STEREO DECODER 

Brochure 4 



£5.19.6 



MW/LW QUALITY TRAN-frj IOC 
SISTOR RADIO TUNER *- d ' ■ **•« 
Brochure 5 



TRANSISTOR CAR RADIO 
Send for Brochure 15 




BRITISH MADE 6-Transistor MW/LW. 
12 volt 3 watt output. Push-button 
wave-change. Boxed, ready to use with 
Speaker and Baffle, Car fixing kit and 
manufacturers' guarantee. Special Bargain 
Offer. Positive or Negative Earth, 
5 Push-button Flfl p P 

de-luxe version Lul - n '' u 4/8. 

£11.18.8. Positive or Negative Earth. 



TRANSISTORS -SEMICONDUCTORS 



COMPLETELY NEW 1968 LIST OF 1000 
types available from stock. Send tor your 
FREE COPY TODAY. (List No. 36) 
•B.c.B.'s from 5/- 

*FTELD EFFECT TRANSISTORS from 9/6 
*POWEE TRANSISTORS from 5/- 

*■ DIODES AND RECTIFIERS from 2/- 
S0 page illustrated brochure as above includ- 
ing Valves and Quartz Crystals. 1/- post paid. 



GARRARD DECKS 

ALL THE LATEST MODELS 




COMPLETE 
RANGE IN 
FROM £5.19,6 STOCK 

Send tor illustrated brochure 16 & 17 



MAYFAIR 
PORTABLE 



ELECTRONIC 
ORGAN 




Also READY BUILT AND 
TESTED 128 gns. 
Deterred terms 
available. 

DEPOSITE36.8.0and12 
monthly payments of 
£9. Total £144.8.0. 
KIT of PARTS Deferred 
terms: DEPOSIT £29.18.0 
12 monthly payments ol £7. 
TOTAL COST £113.19.0. 
ORGAN COMPONENTS 
We carry a comprehensive 
stock of organ components 
for TRANSISTOR AND 
VALVE FREE PHASE 
designs. Brochure 10. 

EXPORT PRICES 
ON APPLICATION 



TOTAL COST TO BUILD 99 GNS. 

Aak for Brochure 8. 

-*■ Build this instrument stage by stage in your own home. 
£ A truly portable instrument for all enthusiasts, 
•k Polly TRANSISTORISED POLYPHONIC. British design. 
ir Call in for a DEMONSTRATION and see for yourself. 

13 NOTE PEDAL KIT £18.0,0. J^PP^ 

HENRY'S RADIO LTD. © 




VHF FM TUNER. Ask for Brochures 3 and 4. 

B7/105 Me/s Transistor Superhet, Geared timing. 
Terrific quality and sensitivity. For valve or 
transistor amplifiers. 4 x 3J x 2Jin. Complete with 
dial plate, o Milliard Transistors, plus 4 diodes. 



£6.19.6 



P.P. 2/6 




FM STEEEO DECODER Broohure 4 

7 Milliard Transistors. Printed Circuit 
Design with Stereo Indicator. For use with 
any valve or transistor FM. Daea pot 
cores to Mullard design and ger, and silicon 
transistors. As used by B.B.C. and (x.P.O. 

Complete Kit Price £5.19.6 P.P. 2/6 



Build a Quality TAPE RECORDER with MARTIN REC0RDAKITS 

383 DECK -k TWO-TRACK. Deck £12.18,6. Amplifier 
£14.18.8. Cabinet and st>aaker 7 gns. Complete 
kits with MICROPHONE and Tin 1,200ft tape, 
spare spool. 




Today's Value £55 32 gOS. P.P. 22/8 

4r POUR-TRACK. Deck £18.18.9. Amplifier 
£15.19.6. Cabinet and speaker 7 gns. Complete 
kits with MICROPHONE and Tin 1 ,200ft tape, 
spare spool . 
Today's Valne £60 35 giTS. PP. 28/8 




T-TRANSISTOR niriAM 

MW-LW SUPERHET IV tW ! 

PORTABLE 
New printed circuit design with full power 
output. Fully tunable on both rnw/lw bands. 
7 translators plus diode, push-pull circuit. 
Fitted 5 inch speaker, large ferrite aerial 
and Mullard transistors. Easy to build with 
terrific results. All local and Continental 
stations. Size 10 x 7 x 3 Jin. 
TOTAL COST £6,19.6 



TO BUILD 



Send for Brochure 1 



P.P. 4/6 



BUILD THESE PRACTICAL WIRELESS DESIGNS 

CLUBMAN 
LESS CHASSIS 
MK I 89/8 

MK II 72/6 

MK HI 45/- 

List No. 41 



LC. F.M. TUNER 


SWITCHED F.M. 


Dec. 19S7 


TONER 


89/3 


Aug. 1967 


Post 2/6 


77/6 


Including RCA CA3014 


Post 2/6 


List 40A 


List 39 



CATALOGUE 



LATEST EDITION 
240 pages, 6,000 items 
1,000 illustrations 

~k 25 pages of transistors and semiconductor 

devices, values and crystals. 
■jr 150 pages of components and equipment. 
i< 50 pages of microphones, decks and Hi-fi 

equipment. 
The roost comprehensive — Concise — Clear 
Catalogue in Gt. Britain. Complete with 
Discount Vouchers Free with every copy. 



components 
10/- worth 



Send today 8/6 IZ 



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